The human brain has three main parts - the cerebrum, cerebellum, and brain stem. The cerebrum is divided into two hemispheres and four lobes. Broca's area in the left frontal lobe controls speech production, while Wernicke's area in the left temporal lobe controls language comprehension. Damage to these areas can result in different types of aphasia. The brain is highly complex and not fully understood, controlling functions like thinking, movement, senses, and more.