There are a lot of things we each need to learn to be successful in the workplace. Some things just need to be memorized and recalled, like which storage closet houses the pens or the light bulbs. But most of what we need to learn is a process, from emailing to filling out paperwork to entering work orders to performing complex data analysis. This is where training comes in.
By definition, brainstorming is a “spontaneous” group activity in which participants try to generate as many ideas as possible, however outlandish, without criticism. Brainstorming can take a lot of forms, and the “spontaneous” part is often misinterpreted as “if you invite people into a room and tell them to brainstorm, then magic will happen.” That (almost) never works. I believe that brainstorming requires a lot of structure and planning to be productive.