The cerebrum, which simply means "brain" in Latin, is the non-technical term for the telencephalon, the largest part of the human brain -- also known as the cerebral hemispheres. It is the most recent part of the brain to evolve, and positioned on top of the more evolutionarily ancient portions of the brain, such as the brain stem. The cerebrum is part of the forebrain, which includes the telencephalon (meaning cerebrum) and diencephalon (the thalamus and hypothalamus). Other regions include the cerebellum and brain stem.
An image of the cerebrum is what most people envision when they hear the word brain. In humans, this region is so large that it dominates most of the volume of the brain. The cerebrum is broken down into four parts -- the limbic system, basal ganglia, olfactory bulb, and cerebral cortex. The majority of neurological machinery implementing our sensory functions and complex learned behaviors can be found in these regions.
The most famous part of the cerebrum is the cerebral cortex, or the surface of the brain. Its characteristic folded surface emerged as an evolutionary tactic to compress as many neurons into as small a space as possible. The cortex is divided into four lobes: the parietal, temporal, occipital, and frontal lobes. Among these lobes can be found the brain areas responsible for processing vision, executing movement, consolidating sensory data, abstract thought, and many other important functions.
Another area of the cerebrum is the olfactory bulb. This phylogenetically old portion of the brain processes smell information and chemical signals such as pheromones. The basal ganglia are portions of the cerebrum located deep in the central hemisphere, made up of so-called "white matter" as opposed to the folded "grey matter" on the surface of the brain. Basal ganglia are nuclei, or transit points for electrical signals, associated with motor and learning functions.
The limbic system is another portion of the cerebrum and is associated with the emotions. Oft-discussed parts of the limbic system include the hippocampus, essential for memory, and the amygdala, which mediates emotions such as fear and anxiety. Put simply, you can think of the cerebrum as the entire brain except for the cerebellum and brain stem.