I am a fan of Texas Holdem Poker. In my opinion, it is the most interesting one. It is not hard to learn the rules of this game, but it will need many games played to understand how it really goes. You will need to be able to read on people's faces to predict what will be they do next round. For example, I always play online on joker123, but when I play in a real casino, I concentrate more on people's reactions, not on my cards. You need to learn how to understand if your opponent is bluffing or not. It is an important skill.
