What are graphs, in computer science, and what are they used for? In laymen's terms preferably.

I have read the definition on Wikipedia:

In computer science, a graph is an abstract data type that is meant to implement the graph and hypergraph concepts from mathematics.

A graph data structure consists of a finite (and possibly mutable) set of ordered pairs, called edges or arcs, of certain entities called nodes or vertices. As in mathematics, an edge (x,y) is said to point or go from x to y. The nodes may be part of the graph structure, or may be external entities represented by integer indices or references.

but I'm looking for a less formal, easier to understand definition.