This technique involves a group of people, usually between five and ten, sitting around a table, generating ideas in the form of free association. The primary focus is on generation of ideas rather them on evaluation of ideas.
If a large number of ideas can be generated, then it is likely that there will be a unique and creative idea among them. All these ideas are written on the black board with a piece of chalk so that everybody can see every idea and try to improve upon such ideas.
Brainstorming technique is very effective when the problem is comparatively specific and can be simply defined. A complex problem can be broken up into parts and each part can be taken separately at a time.