Blackjack insurance is a side bet offered when the dealer’s upcard is an Ace. It allows players to wager up to half of their original bet, hoping that the dealer’s hole card will be a 10-value card, giving the dealer a Blackjack. If the dealer has a Blackjack, the insurance bet pays 2:1, but if not, the insurance bet is lost. While it provides some protection against the dealer’s potential Blackjack, insurance is generally not recommended due to its high house edge and unfavorable odds for players.