This part can be high heels for fashion or to make the person look taller, or flat for more practical and comfortable use.
[1] On some shoes the inner forward point of the heel is chiselled off, a feature known as a "gentleman's corner".
This piece of design is intended to alleviate the problem of the points catching the bottom of trousers and was first observed in the 1930s.
The geometry and material of the heel is an important factor in avoiding slipping.
[3] Rocker shoes have a heel which is more elevated than the sole, and thus does not usually come in contact with the ground.