Freewriting is a tool used to generate a topic.
Freewriting is a popular tool among writers, it is especially useful to overcome something that can become disastrous for them: writer's block. When a writer is struggling to find topics to write about, freewriting can help them out tremendously and you can think about it as a form of "brainstorming" in which the writer does not preoccupy about grammar, orthography or the writing "making sense" they just use it as a "prewriting" strategy to get ideas flowing so they can come up with topics to actually write about.