The brain can be divided into three main regions: the forebrain, midbrain, and hindbrain. Each of the brain regions is associated with a particular type of activity or function, and they are all critical to healthy function of the body. Within the brain regions, there are a number of smaller areas and structures which perform specialized tasks. Together, the parts of the brain make up a very complex and unique organ which has some astounding capabilities.
The forebrain is probably the most well known of the brain regions, because it's "where the magic happens," so to speak. This section of the brain includes the limbic system, thalamus, diencephalon, and cerebrum, and it is part of the brain which is responsible for storing memories and interpreting a great deal of sensory input. Humans have an extremely well developed forebrain, a trait which has allowed for the emergence of language and a variety of other skills. This is also the part of the brain which most people think of when they hear the word "brain," because it makes up the entire top part of the organ.
The midbrain is the smallest portion of the brain, sandwiched between the fore and hindbrain. It is also the most primitive, and it is involved in the relay of information. This section of the brain includes the substantia nigra, a structure which is involved in the process of addiction. Some neurologists may describe the midbrain as part of the brain stem, the structure which connects the brain to the spinal cord and the rest of the nervous system.
The hindbrain, which includes the medulla oblongata, pons, and cerebellum, is found at the lower, back of the brain. It is responsible for controlling involuntary movement and responses to stimuli and is also closely connected with the brain stem. While people wouldn't be able to speak without the forebrain, they can't breathe without the hindbrain, illustrating the vital importance of this area of the brain. This region governs the numerous small and large responses which occur involuntarily over the course of a lifetime to support organ function and keep the body in basic working order.
A great deal of intercommunication occurs between the brain regions. Uniquely, the brain demonstrates a trait known as plasticity, which involves the ability to reshape, grow, and remap itself over the course of a lifetime. As people are exposed to new situations and experiences, their brains are fundamentally altered, whether they are infants with rapidly developing brains, or older adults who may seem set in their ways. Plasticity also allows the brain to remap certain functions in the event that it experiences damage to some parts of the brain regions.