There are six terms we will refer to most of the time in this book: Vertex, Edge, Polygon, Quad, Triangle, and Mesh. Let's see, how we can use them to describe a model of a hand, as shown in the following image:
Let's see what they mean in detail:
Two connected vertices form a line in 3D space, which is called an Edge
At least three points form a "polygon", which is sometimes also called a Face
More precisely, a polygon made out of exactly three vertices is called a Triangle, four vertices form a Quad
The entire hand is composed of several "polygons" forming a Mesh