Knowing the terms of any gaming vehicle is a prerequisite of learning to play well. In the game of Blackjack, there are many terms that have a specific meaning and denote a unique play in the game Doubling Down is such a term.
When a situation favors the player, the player can in certain circumstances increase their bet. The act of doubling down is such a situation. In this situation at many casinos the player has a two-card hand that totals ten or eleven and the dealer shows a break card or at least not a ten. The player announces they wish to double the bet and the dealer hits the hand with only one card. If the deck is rich in face cards the play is a good one as the player has an excellent chance of winning the bet.
There are three possible outcomes from this bet, the hand can win, the hand can lose and the hand can push, tie the dealer. If the hand wins the profit is double what you would have made if you had not doubled down. If you lose both bets are lost. If the hand and the dealers hand tie there is no winner and the hand is a push. Always double down when the deck is rich in high cards and the dealer has a break card showing. Pass on doubling if the deck is rich in low cards or the dealer has a ten-value card showing. Making the extra bet makes a lot of sense when the deck is favorable to the player. It also makes sense to pass when the shoe is favoring the dealer. A rich shoe in low cards is not a good double down situation. Card counters have an edge when making a decision to double down or not.
One other idea, at some casinos the house will let a player double down on any two cards. If this is the case and the dealer shows a break card, the DD is a good play. Know the rules and the favorability of the shoe and you can win at Blackjack.