the central sulcus!

Postcentral gyrus, or the parietal lobe

[Edit: The postcentral gyrus is posterior to the central sulcus, not anterior. The primary motor cortex is located directly anterior to the central sulcus.]

A Ridge/Hill is called a Gyrus (pl Gyri) and a cleft/valley is called a Sulcus (pl Sulci). Some of the Gyri and Sulci are individually named for example look at the cerebrum from a lateral view. You should see one fairly distinct vertical sulcus roughly in the middle of the brain (it will not be straight but reasonably obviously vertical. This is called the Central Sulcus. The gyrus immediately in front of that sulcus is called the Precentral Gyrus and the one behind is called the Postcentral Gyrus. The precentral is where the Primary Motor Cortex is seen and the postcentral is where the Somatosensory Cortex is seen. There are many other named sulci and gyri but it is too complicated to describe them without an image.

If you're referring to the cortex of bone, that would be trabeculae.

The primary motor area is found in the frontal lobe of the brain.