It is the vertex and its plural is vertices
That's a "vertex".
Vertex mate :) 3 or more is a vertex
more is better
An edge is where two faces meet. Imagine a box containing a new mobile phone. The left hand face of the box has 4 edges (front, back, top and bottom) and the right hand face has also 4 edges. But there are 4 more edges where the front meets the top, the top meets the back, the back meets the bottom and the bottom meets the front. This makes 12 edges in total.