The structure indicated is the precentral gyrus.
A gyrus is a ridge on the cerebral cortex, and is usually surrounded by grooves, known as sulci. Fissures are larger than sulci and divide the brain into lobes, as well as dividing the brain into right and left hemispheres.
The sulci anterior to the precentral gyrus is known as the precentral sulcus. This sulcus lies parallel to the central sulcus (also referred to as the fissure of Rolando/Rolandic fissure). The central sulcus separates the parietal lobe from the frontal lobe. The precentral gyrus contains the primary somatomotor cortex.
Learn more about the precentral gyrus in this anatomy tutorial on the basic parts of the brain.