The ad side of a tennis court is the players left side. Or the opponents right side.
It is either ad in or ad out. If the server won the point it is ad in and if the returner won the point then it is ad out.
When serving or returning, there is a deuce side and an ad side. The deuce side is on the right, the ad side is on the left.
ad in, Ashe
ad-out means advantage-out. It usually means that the other person/persons are in advantage of the point, which means if they win the point, they win the game. If you're in ad-out, you need to win 2 more points to win the actual game.
Love 15 30 40 (Game or Deuce) If Deuce, ad-in or ad-out Game
match, point, serve, ad out