Graphs are mathematical objects that are made of dots
connected by lines. Graph Theory is the branch of mathematics that
involves the study of graphs.

Graphs are very powerful tools for
creating mathematical models of a wide variety of situations. Graph
theory has been instrumental for analyzing and solving problems in
areas as diverse as computer network design, urban planning, and
molecular biology. Graph theory has been used to find the best way to
route and schedule airplanes and invent a secret code that no one can
crack.