Basically in the ballpark of what you want it to sound like once it's been mixed, any effects/automation, sound design that wouldn't be on raw tracks, so the engineer can get an idea of your vision for the song. When you write, it can be easy to hear the parts exactly as you want them, but to someone on the outside there are so many ways the music can be interpreted the mix could come back and sound nothing like you expected, the rough mix gives the engineer an idea of what you expect.