Mind mapping is a way to organise concepts (keywords) in the form of a tree diagram where several items (nodes) are surrounding from a central one: the basic concept. Some of the earliest examples of mind mapping are from 3rd century.
Organising ideas (brainstorming), create a classification, reo-organise the structure of a website, take notes during a meeting, prepare a questionnaire, prepare an abstract, to summarize and learn new topics
Mind maps could become too confusing if you have too many concepts to organize. It is probably more suited to the visual/logical learning styles
With a sheet of paper and a pen ( or blackboard, whiteboard, …), or with a software (on computer, tablet, smart-phone)