A heel is the bottom, back part of a shoe or boot that provides elevation. The styling and construction of a heel may vary (i.e., stacked, stilletto, spiked, sculptured, kitten).
About Nubuck:
This is a grain leather that has been slightly brushed on the surface to create a very fine velvet-like appearance. The texture of nubuck is finer than suede.
About Slides:
Slides are a sandal in which the upper does not extend to cover the heel of the foot. The wearer of Slides can simply slip on the shoe without having to tie, strap, or buckle it to secure.