Yes- NPO- (also called BP0 as in beginner) novice Prep-Op
IPO- Intermediate (between 5 and 6) some gyms compete athletes at IPO instead of 6 b/c they feel it better prepares the girls for level 7 than level 6 does. The girls then move to L7 after "scoring out" of JO level 6 often at the first meet of their season after IPO
APO- advanced
They are two different tracks- Prep-Optional and JO. They are not the same, and you can move from JO to Prep-Op but to move from Pre-Op to JO you have to compete and get move up scores. Prep-Op is more "recreational" the judging isn't as hard, skill requirements are different, etc. Currently there are no national standards for Prep-Op like there are for JO.
This is soon to change into a a nationwide system called X-Cel- which should bring more credibility to the program. Right now it's seen as a "lesser" program than JO. At least around here. In Prep-Op there are no compulsaries- you get your own floor routine and floor music, etc. his appeals to older girls especially- or girls who have been in a level for a long time and are just looking for something different. Especially BPO and IPO.
Prep-Op/X-Cel is seen as an alternative to JO to keep girls in the sport longer.
Here's an explanation that helps some- although this person's state calls Prep-op bronze, sliver, gold... etc. Which is another reason for making it a national system. Hope this helps.
A Brief Explanation of Levels in USA Gymnastics | Apex Technical Corner