It's like the last paragraph of an essay where you sum everything up. Touch on the high points/ things that stand out in your memory and clarify them. If anything is still bothering you from the relationship it should be brought up and discussed, but no new material should be put on the table. It's simply closure. You are 'processing' the relationship so you can let it go in the same way you processed your issues earlier in therapy so you could let them go.

This is the ideal of course, how healthy therapy should end. If there are issues you are afraid to bring up and/or just simply can't process in regard the the relationship it's going to follow you around for years... (Ask me how I know)

But then again, staying in a bad T relationship will never solve those issues, merely add to them. If that's the case it's better to get out while you're ahead, but it is so hard to see the truth when you're trapped in distortions. (Again, ask me how I know...)