Question: what do the brain cells do and why

Robert Lees answered on 14 Nov 2015:

Brain cells send signals between each other and to the ‘peripheral’ nervous system (not in the brain or spine) to keep us alive and reacting to changes (for example, fear or digestion).

We are able to store memories and make decisions, feel emotions etc. because of our brain cells signalling to each other. A popular theory is that a thought is held by a group of cells in a network with each other. When turned on, these cells signal and you recall everything to do with that thought.