A system of brain nomenclature created by the 19th century German anatomist Korbinian Brodmann
Brodmann divided the cerebral cortex into 47 distinct regions based entirely on the differences in cellular structure. As the study of neuroanatomy became less focused on structural classification and more focused on functional classification, it was discovered that Brodmann's areas, (derived totally from structural inspection,) correspond almost exactly to specific brain functions as determined by various brain mapping experiments. For example:
Brodmann's areas 17-19 are located at and near the occipital pole, the farthest posterior (behind) point in the brain. They compose the visual cortex, the area of the brain responsible visual processing. (Remember, all that you "see" begins as a spotty pattern of light falling on the retina. Cognitive scientists have been trying to reproduce human visual processing for years with only marginal success.)
Brodmann's area 4 is located at the precentral gyrus, -- a strip of gray matter on the outer surface both sides of the brain that runs roughly from ear to ear across the top of the brain. This region is known as primary motor cortex because the neurons there (more or less) directly control your muscular movements.
Brodmann's areas 9 and 10 are known as prefrontal cortex, located at the very anterior (front) of the brain. This brain area is the most complex, least understood and most highly developed part of the human brain. It is the region most associated with higher cognitive functions, such as reasoning, planning and attention. When lobotomies were popular, this was the region of the brain that was destroyed.
Of course, its important to remember that no brain region is an island - e.g. none of these areas named could do their work on their own, and brain function in general relies on the heavy interconnectivity of the parts of the brain. As recently as the early 20th century, the idea that cognitive functions were localized to specific brain regions was still somewhat controversial - making it so much more a stunning discovery to find localized function so closely associated with a purely structure-based mapping technique.