The brain is a soft, gelatinous organ made up of multiple folds. Most of the brain, around 85 percent, is taken up by the cerebrum. It is this structure that gives the brain its distinctive shape of two halves - the right and left hemispheres. The two hemispheres of the brain are connected by a thick band of nerve fibers called the corpus callosum. The brain halves are able to communicate with each other via this "bridge."

Source: Better Health