What exactly is the central nervous system and what does it do?

Brain and spinal cd: The central nervous system consists of the brain and spinal cord. It serves as the receiving and processing plant for outside stimuli and the point of reasoning and production of action/response. It consists of things like cognition and relaying sensory information, as well as regulating the day to day management of bodily functions.

No problem: If you want to find out more than can be covered in 400 characters, you can start with one of the standard references: Principles of Neural Science, by Kandel and Schwartz. I have the 5th edition. It's 1709 pages long. It covers the basics. It's an introduction. If you really want to get into the subject, there are more and bigger books you can read.