Revising does include proof reading and editing but it is much more than that. It takes any time from a week to months. Editing for structure. For flow. For holes. For cutting a lot of prose. For characters and setting. For better plot.
When all of that editing is done, you've then completed the mammoth task of revising. If you've done it wisely, then the wood ought to be polished, it ought to shine like gold. And it will too, if you've got a great work in the first place.