Ken Alcock has written a detailed FAQ explaining what all the files in Opus's configuration folders do, how they are backed up, and so on.
This is a great guide if you want to dig into the config details beyond what the automatic Backup & Restore feature in Opus will do.
I'll just give you a link to the FAQ, instead of copying the text to here, as duplicating the formatting would be a pain:
HOW TO: Back-up or locate your Opus configuration (Advanced)
BTW, this FAQ is a companion to the older one: HOW TO: Back-up or locate your Opus configuration (Simple)