What is Brainstorming?
Brainstorming (in writing) is the process of generating the ideas that you want to focus on in your paper. When you're brainstorming, you can come up with a bunch of different ideas, ideas that build off of one another, ideas that excite you, and then when you are done, you can narrow all those ideas down to your favorite or the one you are most passionate about. You can also combine several of your ideas if you cannot just pick one!
There are a lot of different ways to engage in the brainstorming process - try brainstorming on these Google Docs and see which way works better for you.