I think it's been mentioned before, but I'm not sure where....so here's the information
Levels 1-3: beginner levels, competition are a few each year
Level 4-6: Compulsary levels--everyone does the same skills
Level 7-10: optional--everyone must meet certain requirments but may fulfill them doing a variety of skills
Elite: Olympic level
Level 1: extreme beginner--forward rolls, backward rolls, etc
Level 2: little more advanced---roundoffs, pull overs on bars
Level 3: front mill circle on bars (one leg over bar and go around in a circle forwards). learning backhandspring on floor. handstand on beam, etc
Level 4: first USAG sanctioned competitive level
Floor: handstand forward roll, back extension roll to pushup shape, round off backhandspring, etc
Vault: handstand flat back on a whale mat
Bars: front hip circle, cast back hipcircle, front mill circle, undershoot (underswing) dismount
Beam: handstand, side handstand, basic jumps, half turn
Level 5: roundoff 2 back handsprings and a front handspring on floor. cartwheel on beam, kip and long hang kip on bars (use of high bar). front handspring over vault table
Level 6: back tuck and front tuck on floor, back walkover on beam, fly away dismount off bars, etc
Level 7: back handsrping and round off on beam, back layouts on floor, back giants on bars, etc
Level 8-10: skill difficulty increases.
If you'd like some examples of skills for levels 8-10 just let me know.
Also, after level 10 is the elite level which I describe as the olympic level.