The most famous regions are Sanani, Harazi, and Matari. All of them are labeled “Moka” (or Mokka, Mocca, Mokha) because that is the varietal of coffee plant which Yemen grows. The only other place that grows Mokka is Ethiopia Harrar. A farmer in Guatemala managed to harvest 8 pounds of Mokka and sold it for $505/lb because of how rare it is to grow the varietal outside of the middle-east region. All three regions are known for undertones of bitter herbs and cocoa, but the Harazi is generally considered the most desirable region, and the Sanani is the most common (although no coffee from Yemen could really ever be considered "common")