The cerebrum is an umbrella term encompassing the frontal, parietal, occipital, and temporal lobes. And fittingly, it looks much like an umbrella, cupped atop the brain stem and other goodies. It is this umbrella that makes humans human.
According to paleoneurologists, the first structure we’d call a brain emerged in reptiles about 500 million years ago. It was little more than a brain stem, capable of maintaining bodily functions, foraging for food, and mating (much like pubescent males). This “lizard brain” remains much unchanged in humans and other mammals; almost all advances have been in the area of the cerebrum.
Interestingly, in mammals, the size of the cerebrum and even the number of neurons it contains may have less to do with intelligence, emotion, and higher-order thinking than do its folds and the density of its connections. A folded cerebrum offers significantly more surface area for the organization of specialized processing centers. And adding a handful of neuronal connections increases the potential pathways of information through the brain much more so than adding a handful of neurons themselves.