Shouting “Blackjack!” when playing the game makes the situation obvious. What makes a blackjack is 10 and 11. Two cards you are dealt need to equal to a total of 21. You can make a blackjack from tens (ten, jacks, queens or kings) and an ace (which has either the value of 1 or 11).
Blackjack is often considered a game of chance, but in reality for professional players it’s a strategic mathematical game.
When using one deck, blackjack is a game of chance because most rules say that all cards should be faced down. It becomes mathematical when when two or more decks are used, because according to most rules the cards are dealt face up, which means that players know the cards that have been dealt and played, and therefore winning strategies can be used.
The most common and consistent winning strategy in blackjack is card counting. There are many ways of doing that. For example if you’re playing with two decks and all 8 aces have been played, you know that the casino dealer cannot possibly get a blackjack, which is an advantage for you.
In some land-based casinos card counting is not allowed and players can even get banned for using this strategy. It is okay to use it in online casinos, but you need to be very quick because there’s a time limit. Some ways of card counting are very complex, so to be fast you need to be very good at calculations.
Blackjack can definitely be compared to poker since it’s also a mathematical game and card counting strategies can be used.