What is pascal wager?

Pascal's Wager (or Pascal's Gambit) is a suggestion posed by the French philosopher Blaise Pascal that even though the existence of God cannot be determined through reason, a person should "wager" that God exists, because a person has potentially everything to gain (by going to heaven, getting God's favor), and nothing to lose (if God does not exist, at least you led a good life following morals..you weren't really disadvantaged by it).