What is concept mapping?

1. Graphic.org has a nice brief definition and links to other explanations, including by Joseph Novak, concept mapping's pioneer

A concept map is a special form of a web diagram for exploring knowledge and gathering and sharing information. Concept mapping is the strategy employed to develop a concept map. A concept map consists of nodes or cells that contain a concept, item or question and links. The links are labeled and denote direction with an arrow symbol. The labeled links explain the relationship between the nodes. The arrow describes the direction of the relationship and reads like a sentence.

2. Wikipedia too provides a nice definition:

Concept mapping is a technique for visualizing the relations between concepts. Its purpose is to form or assess a person's cognitive map. A concept map is a diagram showing the relationships between concepts. Concepts, like "tree" or "plant", are connected with labelled arrows, for example ("is-a", "related-to" or "part of"). The addition of labeled and flexible links (attached during or after construction) has been found to significantly improve the level of meaningful learning and communication of the concept mapper.