‘Pantsers’ write by the seat of their pants. They just sit down and start writing. They normally end up doing a whole lot of revision and rewriting and, occasionally, even changing the thrust of the story, but they say this method allows their mind free rein and results in a better product.
‘Plotters’ outline their novel and describe their characters and often describe and research the setting before beginning. They are comfortable doing this because they know who the story is about, where it’s going, how it’s going to get there, and why they are writing it in the first place. They usually spend less time changing and rewriting but that’s balanced by the extra time they put in before beginning.
So it just depends on which kind of writer you are.
I started out being a ‘pantser’ and ended up being a ‘plotter’ when I realized I was writing pages and pages of beautifully worded fluff that said nothing and went nowhere.