Not just you. When I first started to hobby, and before I found this site, there were a lot of terms I needed to be caught up to speed with. Urban Dictionary was a godsend.
This sure as hell ain't the first thread/post about acronyms, and ain't gonna be the last. As long as acronyms are gonna be used, questions will be asked as to WTF? Get used to doing your research. It'll save you a lot of grief and some cash along the way.
Now you have your first review and reference, you can see the ROS in reviews. What you need next is a P411 membership and you'll be GTG.