Prewriting means just what it says—it’s the writing that occurs before you actually write a draft. Richard Nordquist writes that
“In composition, the term prewriting refers to any activity that helps a writer think about a topic, determine a purpose, analyze an audience, and prepare to write. Prewriting is closely related to the art of invention in classical rhetoric.
‘The objective of prewriting,’ according to Roger Caswell and Brenda Mahler, ‘is to prepare students for writing by allowing them to discover what they know and what else they need to know. Prewriting invites exploration and promotes the motivation to write’ (Strategies for Teaching Writing, 2004).” 
In order to explore and identify what might be fruitful ideas for writing, I tend to jot concepts, phrases, and notes to myself. Sometimes I draw linkages to connect related ideas. Other writers tend to just write in order to explore and identify patterns of thought. Still other writers list out all of the concepts and information they can think of around a certain topic, and then narrow and refine their lists. Others start writing a really “drafty draft” of an essay, and then circle back into prewriting strategies to develop ideas. Any prewriting strategy is fine, depending on “how your mind thinks” and how you like to discover and explore ideas.
(text from here to end of page © Empire State College)
How do writers develop ideas for writing? Writers use many techniques, and it’s a bet that most of the techniques involve writing itself. Think of a composer creating ideas for a song by playing notes on a piano keyboard. Think of a sculptor creating ideas for a statue by shaping and reshaping pieces of clay. Think of a quilter creating ideas for a quilt pattern by arranging and rearranging different snippets of fabric. All creative endeavors go through preliminary stages in which creators generate ideas, discard some, and play with others that capture their imaginations or that seem to “fit the bill.” Each creator develops ideas by getting immersed and “doodling” in the particular medium. And writing is no different. In writer’s terms, that preliminary stage of idea development is called “prewriting.”
Prewriting usually is messy in terms of having ideas scattered all over the place–think of the quilter with pieces of fabric all over the living room floor. For a lot of people, it’s liberating to be messy and not worry about logic, pattern, or final form. That’s the purpose of prewriting, to be as free-ranging as possible in generating ideas. If you’re aggravated by mess, then prewriting can be thought of as pre-planning, as a means of generating the ideas and data that will help you create the essay draft. Either way, prewriting is a stage of idea incubation, a way to generate ideas and capture your thoughts through writing.
Ideas for writing develop in many ways, and prewriting techniques reflect the different ways in which ideas can develop. Some forms of prewriting are intended to help you bring subconscious ideas and interests into consciousness (some forms help if you tend to draw a blank when you’re asked to “write about what interests you”):
- Maintaining a personal journal
Other forms of prewriting are intended to help you generate your own ideas in response to others’ ideas:
- Responding to a text
- Maintaining a response journal
Still other forms of prewriting are intended to help you both generate and focus ideas about a subject that you’ve already chosen:
- Asking questions about a subject
- Making a list
- Idea Matrix for College Writing
- Working with Prewriting
The following videos explain different strategies for prewriting. Although you’ll read about these strategies and more in the upcoming pages, these videos provide a good introduction to some basic approaches to prewriting.
 Nordquist, Richard. “Prewriting (Composition).” Glossary of Grammatical and Rhetorical Terms, ThoughtCo., 6 Mar. 2017, www.thoughtco.com/prewriting-composition-1691676.