A future bet is a bet on an event that will be decided in the future, sometimes weeks or even months away from the date your bet was placed. In most cases a future bet will involve the end of a full season of a sport type.
For Example: The team to win the Super Bowl, the player to win MVP of the season in NBA or the number of wins a team will have at the end of the season. These are just some examples of the many future bets that can be offered.
One simply needs to have bet on the correct team or player in order to win the bet.
Because of the difficulty involved in correctly guessing the outcome of an event so far in advance, you will usually find that the odds for futures will be (+) numbers.