Brainstorming as a method can be used for:

Brainstorming is used for generating many new ideas in an area of interest, freely and without immediate criticism.

Out-of-box thinking is a quality that may result from brainstorming, but not the method's defining purpose of idea generation.

Coherent thinking is orderly, logically connected thought, the opposite of brainstorming's free flow.

Critical thinking is evaluative and convergent, whereas brainstorming is generative and divergent.

Brainstorming was introduced by Alex Osborn, who urged deferring judgement to boost the quantity of ideas.

Its core rules are quantity over quality, no criticism, welcoming wild ideas and combining them.