When you look at the bottom of the hoof you’ll see the frog down the middle, surrounded by the sole. My ponies’ feet are like Memphis, they have a lot of sole. The outside is covered by the hoof wall. Around the sole there is a thin line, that thin line separates the sole from the hoof wall.
The heel is a soft part at the back of the hoof (the heel faces the horses butt if the hoof is flat on the ground).
With the hoof flat on the ground you can see and feel a slight hump around the top of the hoof where the soft flesh meets the hard hoof wall, that line is called the coronary band.