These are the standard abbreviations for the six men's artistic gymnastics events, listed here in Olympic competition order. Whenever you're at a sanctioned USAG meet, this is the order the rotations will follow.
FX: Floor Exercise
PH: Pommel Horse (and mushroom)
SR: Still Rings
VT: Vault (Table)
PB: Parallel Bars
HB: Horizontal (High) Bar
The All Around Score (AA) is the combined score from all six events.