Handicap Betting is a type of betting in which teams or players are handicapped according to their form so that a stronger team or player must win by more goals or points for a punter betting on them to win.
For example, if Manchester City are clear favourites to win home against Leicester and you bet on Manchester City to win with a handicap of (0-2), this would mean that Leicester receives a 2 goal 'virtual head start' in your bet, effectively leading the game before it starts.
In order for your bet to win in this case, Manchester City would have to win the game by 3 or more goals difference as all bets will be settled according to which team wins the match after the handicap line has been applied.