Card counting is a way that blackjack players can give themselves an advantage. The idea is based on the idea that the player has an advantage when there are more tens and face cards in the deck and the house has an advantage when there are more low cards in the deck. As the game gets played and cards are dealt out the composition of the deck changes, this is what card counters are trying to take advantage of. They will increase the amount the bet when the odds are in their favor and reduce the amount that they bet when the odds are in the houses favor.
While it is possible to give yourself and advantage with card counting actually doing it is very difficult. The really hard part is keeping the count straight. There are various different systems that can be used to count cards but they all require that you count all of the cards that get dealt. The challenge is that there are usually several players and you have to be able to see what cards they are dealt. In addition you have to keep the count and make sure that you play with proper strategy. The game moves very quickly and there are few people who are able to do this.
The other challenge that you will face is that the casinos have gone to a lot of effort to reduce the advantage that you get from counting cards. The original idea was developed when the games were played with only one deck. This case there was a pretty significant advantage to counting cards. Nowadays most casinos will use eight decks which reduces the advantage dramatically. The more decks that are used the less the advantage that you will get from counting cards.
Another issue that you are going to face when you are trying to count cards is that the casinos do not allow it. That means that you have to be able to count without them noticing that you are doing it, not an easy thing to do. In addition if you alter your betting pattern based on the count the casino will likely not allow you to continue playing. You need loads of practice in counting cards, in knowing where the dealer cuts the cards (plastic cards are thicker so practice with regular cards!) and even learning how to make your betting look natural!
The reality of card counting is that although many people try it because they think they can get an advantage from it very few are able to do it successfully. While the casinos are opposed to card counting they actually benefit from it, one of the reasons that so many people play blackjack is that they think that they can be beat the system. In reality the vast majority of card counters end as losers just like everybody else who plays at the casino. Unless you are really good at it you probably shouldn’t expect to make money by counting cards.