An edge.
a face is 1 side of a geometric solid.
The side of your face is called the profile
It is called the face
Face
An edge.
It is called the profile
Slip face.
The cheek The Temple or as a side view, the profile.
To answer this question more details need to be provided. For example one a 3D shape one side is called a face.
The steep side of a dune is called the slip face. It is the side of the dune where sand grains are deposited as they slide down due to gravity.
a plane
a line