Brainstorming is a group discussion technique used to generate ideas and solve problems. It was invented in the 1930s and involves spontaneously contributing ideas without criticism. Effective brainstorming requires a clear problem definition or "brief" to focus on, diverse participants, and a structured yet creative process. The process includes establishing ground rules of aiming for quantity over quality, welcoming unusual ideas, building on others' contributions, and using techniques like creative prompts to spark new thinking when ideas are lacking. The goal is to produce many ideas that can then be evaluated and refined into promising solutions.