Mine goes through a few steps. I'll use this recent illustration as an example.
First when I'm working out a pose or composition I'll do really small thumbnail sketches like these while I try to think through what I want. These were the unused ones for this pic that I dumped on a layer to turn off:

Once I figure out what I want to draw I'll do a "rough sketch" layer. I've taken lately to sketching in a few different colors as I develop different parts of the picture or character. It helps to differentiate things when I go to ink. The rough sketch is also mostly just for proportion/anatomy. I try to avoid going into too much detailing or clothes at this point.
My last sketch is the "clean sketch" layer. This is where I add in aforementioned omitted detailing using the rough sketch as an underlay:
skipping the middle steps, this was the final art:
This was a standalone illustration, but I go through similar steps on my comics as well 