In blackjack, insurance is a side bet offered when the dealer's upcard is an Ace. It allows the player to bet up to half of their original wager to protect against the possibility of the dealer having a blackjack. If the dealer does have a blackjack, the insurance bet pays 2:1, but if not, the insurance bet is lost. While it may seem like a way to safeguard against the dealer's blackjack, insurance is generally not a good long-term strategy, as the odds of the dealer having a blackjack are lower than the payout, making it a bet with a higher house edge.