GraphThing is a tool that allows you to create, manipulate and study graphs.
These "graphs" are mathematical objects (look at this introduction to Graph Theory) that describe relationships between sets; they are not 2D plots, charts, or anything similar to that.
At the moment, only support for simple graphs and digraphs are supported; that is, no multiple edges or loops. Other than this, GraphThing can handle every type of graph. Below is a brief list of some of the main features of GraphThing: