I doubt that there's a definitive answer to this. Different writers have different styles and different things that work for them.
Personally, my approach is that for the first draft, I just throw words on paper. Whatever comes to my mind I type into the computer. Once I have a whole bunch of words down, then I go back and clean it up. I rewrite sentences that are poorly worded, re-arrange sentences or paragraphs so that the flow of the thought makes sense, drop text that doesn't really advance the thought, and add text when there are gaps.
When I was young and the idea of owning your own computer was in the same league as owning your own jet airplane, I wrote with a typewriter. Then, once you typed a word, if you changed your mind you had to throw away the whole page and retype it. If on page 10 you decided that you needed to add a paragraph to page 4, you would have to retype page 4, which would push some text from that page onto page 5, so you had to retype page 5, etc. So back then I would type a first draft, make notes on it and scribble all over it, and then type a second draft, and declare myself done.
Today, with word processing software, I go back and forth through my work constantly. It's easy to add or subtract a word or a sentence and let the computer adjust all the following pages. Do it. Hack and chop and go forward and backward and move things around. It's easy today. I don't really make "drafts" anymore, like first draft, second draft, third draft. Rather, it's an ongoing process, change a little here, change a little there, until I'm satisfied that it's the best that I can produce. (Or until I'm sick of reading and re-reading my own work.)