Freewriting
Freewriting is the practice of writing down all your thoughts without stopping, and without regard for spelling, grammar, or any of the usual rules for writing. It might include a topic as a general guide, or it might not. The purpose of the exercise varies, but it can be used to generate ideas and to clear out distracting thoughts. There are various possible forms of freewriting, such as journals, essays, and fiction writing.
When you freewrite in your journal, you write down anything that comes to mind. You might decide to set a limit, such as the number of pages or a time limit. Freewriting in your journal is different from reflecting and working through a problem. When you freewrite in a journal, every random idea and impulse goes on the page, and you should write without stopping. You might encounter an idea that you want to explore during the freewrite, and this is an impulse that you should follow. The main thing is to not begin the freewrite with any topic in mind.
Freewriting is also a prewriting or discovery activity. For example, your instructor might ask you to write down your topic at the top of an empty page, and write for five or ten minutes without stopping. This process helps silence the inner critic that stifles the flow of ideas and creativity. Writing instructors often begin each class with a freewriting activity, to help students remain focused.
If you write fiction, the freewriting process can help you break free of perfectionism and writer's block. Freewriting helps do away with judgments about good or bad writing. Anything is allowed, but you might want to tear up some of it later for privacy reasons! You can begin with a prompt, or imagine the best and worst things that could happen to your protagonist as a way to get started.