Orchids from the Paphiopedilum, Phragmipedium, and Cypripedium genera (that’s plural for “genus”) are called “slipper orchids” or “ladyslipper orchids” because the shape of the pouch (a.k.a. lip or labellum) resembles a slipper pointing toe-downward.

As you can see in the picture, there are many different types and colors, but they all have the distinctive “slipper” pouch.