I'm gonna make a bold claim and say that you are your brain. Everything you think, feel and experience happens in and is possible solely because of your brain. Your consciousness arises there, your love resides there, your annoyance at the neighbour's dog barking in the night is also situated there (although many philosophers of mind would fight me on that reductionist view). So learning some basic things about our Lord Commander of the Mind Watch (sorry) doesn't seem like a bad idea to me.
1. Neurons and how they talk to each other.
First of all, our brain is not a mush of identical cells mysteriously keeping you conscious (although you can't deny the wonder of consciousness is a bit mysterious). It is a mixture of thousands of different nerve cell types working on specific functions. Some of them transport the sensations from your eyes, ears, fingers, gills, wings or whatever to your brain and are accordingly called sensory neurons; some carry your intention to move to the muscles and are called motor neurons; and finally there are nerve cells that are dealing with everything else (which is a lot), called interneurons.
And my personal favourite: Purkinje cell which makes sure your motor coordination is on point.
The communication between these tiny thingies is crucial for your, umm, everything, so let's see how exactly they do it. Basically, they send electrical signals using chemical substances (this sounds pretty much sci-fi already and we haven't even properly started yet). When a neuron is activated, an electrical signal (called action potential) travels all the way through until it reaches a synapse: a tiny gap between two neurons where the information exchange actually takes place. This electrical signal makes the active neuron release neurotransmitters which tells the receiving neuron what to do next (to become activated too or rather to stay passive) into the synapse.
Say a cell notices there is a nice sandwich in front of you. It gets activated and sends some dopamine to another cell which, in turn, knows that dopamine means that a reward is expected. This computational process in your brain makes saliva fill your mouth in joyful expectation.
Now there are some numbers which are as incomprehensible to me as why people love Kanye: there are about a hundred billions neurons in the brain. And this electrochemical process I just described? It happens in fractions of milliseconds. Moreover, an average neuron is connected to thousands other ones meaning a total of about hundred trillions synaptic connections in total. However, even though these numbers sound astronomical, beware of the common myth about "more synapses in the brain than stars in the Universe" as it's not true (what is true though is that number of our synapses surpasses the number of the stars in our galaxy. In your face, Milky Way).
2. What is the brain made of?
As our brain developed in an inside-out fashion, its oldest parts lie deepest within our skull. And when I say "old" I mean it: we share these parts of our brains with our remote relatives that have conquered land around 320 millions years ago. Their main functions are quite simple (but still able to save our ancestors' asses and allow us to exist): it makes sure our heart is beating, our lungs are breathing, our temperature is regulated and so on. This part goes by the name "brainstem". If i throw a stone at you you're gonna duck your head without much conscious thinking -- your anciently wired reflexes did that for you. You never need to remind yourself to breathe (unless you're talking to Beyoncé) -- your million of years old wiring is responsible for that too. Just next to the brainstem another ancient structure lies -- the cerebellum, literally meaning "the small brain" (it really does look like a mini-me of the brain). It makes sure your movements are well-coordinated and fine-tuned and you don't move like a robot whose circuits have just exploded. It constantly compares what movement you actually wanted to perform and what your limbs are really doing and interferes if there is a mismatch. Cerebellum is also your guy when it comes to the accuracy of your movements and motor learning -- when playing darts, for example, you should thank it for your improving performance. With every throw it adjusts your movements a little bit more until it finds the right position.
Some time later (and we are still talking millions of years) new structures developed around brainstem (you can very roughly imagine it like putting a second ice cream scoop on top of your brainstem). These parts provided our ancestors with basic emotions and motivation ("this food was good. I feel good about this kind of food. I will approach it next time I see it. This predator, on the other hand, was bad. I'd better avoid it"), as well as the fight or flight-response and gave them an opportunity to learn from the experience and thus anticipate stuff instead of merely reacting to it. I mean, look at a crocodile who doesn't really have this brain part. Does it seem like it has a rich emotional life? Yeah, I thought so too.
These brain regions are called the limbic system (although, a lot of scientists argue that this term is misleading and it is not an independent system per se). Some prominent names you should know (and at least pretend you know what they mean) are amygdala and hippocampus. Amygdala is the small thingy most commonly associated with the fear processing, aggression and connecting memories to emotions -- if you remove amygdala from mice (or even people) they become very tame and stop reacting to something that would have caused rage or fear otherwise. Hippocampus is this sea-horse looking structure which makes your long-term memories happen. H.M., one of the most famous neuroscience patients whose hippocampi were removed on both sides could remember things which happened to him in the past, but was completely incapable of forming new memories (that is, he suffered from anterograde amnesia). So an hour after having a fight with a nurse he would friendly greet her and ask her who she was. Interestingly, this impairment only affected his conscious (declarative) memory, but spared the learning of new motor skills. He could learn how to perform a complex motor task, but wasn't aware of ever doing so.
The last to emerge was the part you usually think of when you hear the word "brain": The cerebral cortex with all its wrinkles and grooves. This is the final ice-cream scoop covering all the deep brain structures we’ve just talked about. The general thing you need to know about the cortex is that it is divided in two hemispheres, each consisting of four regions (or “lobes” as us scientists call them).
The smallest lobe located at the very back of the head is called “occipital lobe” and it’s all about vision. Visual signals travel all the way from your eyes through the whole brain to end up there and to be made sense of and consciously experienced. If you damage this region your vision could be affected in a variety of ways: Might be that you cannot see colour or perceive motion anymore, might be that you lose the access to the meaning of the objects you see -- you know you’re seeing a metal thingy you normally you for eating but you have no idea in hell what it’s name is (this is called “visual agnosia” btw). The lobe hiding behind your ears is called “temporal lobe”. Its most prominent function is to deal with hearing and language comprehension. It also has plenty of additional purposes such as working on rhythm, pitch and other aspects of music processing and allowing you to appreciate Taylor Swift (or whatever cool tunes kids are into these days) and storing concepts and meanings of the words. If you’re unfortunate enough to have this lobe damaged you might experience things that would really mess up your life. There is auditory agnosia, meaning that you can perceive sounds but have no idea what they mean, like hearing a police siren and not connecting it to any meaning, and then there is receptive aphasia, meaning you cannot really understand speech and also you have troubles with saying meaningful things.
The third lobe is situated over the temporal regions and is called “parietal lobe”. It is the home of your somatosensory area which brings you all the physical sensations from inside and outside your body. This lobe allows you to experience the touch of soft kitty’s fur, the pain of bumping your head and the aching muscles from yesterday’s workout. And I bet you would be surprised if I said this handsome young man stands in a direct relationship with your sensation-perceiving region.
This guy is called “sensory homunculus” and he symbolizes how your body is represented in the brain. In the somatosensory cortex there is a distinct area for each of the body parts which processes the sensations coming from this respective part. And as you might have noticed, your lips are much more sensitive than your heels; accordingly the areas responsible for lips take more space in the brain (and on the homunculus). Apart from that parietal lobe is really important for attention (especially in the right hemisphere). If the right parietal cortex gets affected by a stroke or some other shitty thing a condition called “neglect” can arise. And, well, it is exactly what it sounds like: you neglect one side of your world (left, to be precise). You don’t groom, shave or apply make-up to the left side of your face, you ignore the left half of your world or even not recognise your left limb as belonging to you.
The last but absolutely not the least region is called “frontal lobe” and it is essential for what you call your personality and sense of self. These areas are not concerned with some plebeian tasks like sorting out primary sensory information; they are responsible for what is called executive functions: planning, decision making, controlling your emotions, putting attention to the right place and problem solving. Damage to these areas will not produce any crazy and immediately noticeable impairments like neglect or agnosia but it will fuck you up in a more sneaky way. Consider Phineas Gage, a guy who had a big iron rod going all the way through his skull destroying pretty much his whole left frontal lobe.
An amiable and hard-working fellow before the accident, Phineas turned impulsive, could not stick to his plans and the balance between his “intellectual faculties and animal propensities” seemed to vanish. However, his intelligence level, memory and general functioning were not impaired (he even went to a doctor right after the incident, clearly describing everything that happened and sneezing out parts of his brain as he went), making his personality the only victim of the accident. Frontal lobes are truly versatile: they are indicated to have weaker connection with amygdala (and thus weaker control over emotions) in anxiety patients, to define which experiences will be transferred into long-term memory and which will be forgotten and much, much more. Another thing residing in the frontal lobe is your motor cortex, the region that sends signals to your muscles and makes movement possible. And it has a lot to do: Even a seemingly easy task like picking up a sandwich requires a lot of calculations, such as which muscles to use in which order, which force is needed to pick it up etc etc. Fun fact: We once thought that it would be much more difficult to teach a robot how to play chess than how to run. Well, Deep Blue already won against Kasparov while our attempts at making robots move meaningfully look like this (a lot like me in the gym class in high school tbh):
So all in all, if you ask me, the question of how this slimy blob of fat allows us to comprehend mysteries on the Universe and ponder on the meaning of life is still the most mind-blowing ever.