A mind map is a diagram used to represent words, ideas, tasks, or other items linked to and arranged around a central key word or idea. Mind maps are used to generate, visualize, structure, and classify ideas, and as an aid in study, organization, problem solving, decision making, and writing.
To make the concept more clear I've made a Mind Map of the MIND-MAP concept, given below:
You can get more information on Wiki: http://en.wikipedia.org/wiki/Mind_map
