I'm pretty sure this is the first year the NBA has kept these stats officially. +/- is the difference in points scored by the team when a player is on the floor. For example, if Lebron James plays 40 minutes in a game and the Cavs score 15 more points than the Bucks during his 40 minutes on the floor, his +/- for that game is +15.
BA stands for blocks against. It shows how many times a player's shot is blocked during a game.