Cerebrum, or forebrain, is the largest part of the brain, composing about 70 percent of that organ.
Cerebrum is situated beneath the roof of the skull and consists of two hemispheres that are separated lengthwise by a layered division. The outer layer of each hemisphere is the cerebral cortex, the section of the brain sometimes referred to as “gray matter.”
Within the cerebral hemisphere is white matter consisting of three kinds of fibers that connect the hemispheres, convey impulses to and from the cortex and the spinal cord, and connect different areas of the cortex with each other.

What does the cerebrum do?

The cerebrum performs a variety of tasks, including controlling the sensory and voluntary motor functions, as well as such higher processes as thought and memory.