PPR = Point per reception. An optional method of scoring which gives a fantasy point for catching a pass. This boosts wide receiver value in relation to running backs, and boosts certain running backs that also catch passes.
Deep league = a league with either large rosters and bench size AND/OR a league with 14+ teams in it. If you consider a "standard" 12-team league to have an active roster of QB, RBx2, WRx3, TE, K, DEF and 5 bench spots, that's 14 players per team. Thats 168 NFL players on rosters across all teams. If you have a league that has more teams or larger rosters, less NFL players will be in the free agency pool. The each team will have to make do with lesser quality players because the good players are distributed across more teams. For example, a mediocre fantasy player like Peyton Hillis may not be a starting roster player in a "standard" league, but will be in a "deep league".