Face

The visible surface spanning three or more vertices.

A face is the filled polygon that actually renders. The minimum number of vertices needed to make a face is three (a triangle). Four-vertex faces are quads, the preferred working shape for modeling, and faces with more than four points are called n-gons, which are fine on flat surfaces but unpredictable on curved ones.

Related: Tri (Triangle) · Quad · N-gon · Vertex

These fundamentals are covered hands-on in Blender Geometry Essentials 01, free with a free account.