Graphs
Definition: A graph is a collection of things (usually called vertices) together with a collection of pairs of vertices (called edges)
Note: Edges are NOT geometric => no specific shape, form length
Graphs can/do have many different visualization
A simple graph is the one without loops, without multiple edges.
The degree of a vertex, deg(v) = 2 x # of loops based at v + 1 x # of nonloop edges involving v
