Writing is the process by which you realize that you do not understand what you are talking about. Importantly, writing is also the process by which you figure it out.
Writing about something teaches you about what you know, what you don’t know, and how to think. Writing about something is one of the best ways to learn about it. Writing is not just a vehicle to share ideas with others but also a way to understand them better yourself.
Paul Graham put it this way: “A good writer doesn’t just think, and then write down what he thought, as a sort of transcript. A good writer will almost always discover new things in the process of writing.”
There is another important element to writing that often gets overlooked. Writing requires the compression of an idea. When done poorly, compression removes insights. When done well, compression keeps the insights and removes the rest. Compression requires both thinking and understanding, which is one reason writing is so important.