Brainstorming, free writing, keeping a journal and mind-mapping are examples of divergent thinking. The goal of divergent thinking is to focus on a subject, in a free-wheeling way, to think of solutions that may not be obvious or predetermined. All ideas are valid for idea stimulation in divergent thinking.
Divergent thinking is the opposite of convergent thinking, which involves solving problems through obvious choices only. One would use convergent thinking to answer multiple choice tests on an exam, but use divergent thinking methods to answer an essay. Convergent thinking is considered black and white, while divergent thinking has gray areas.