According to the historians’ statements and to the archaeologists’ testimonies, games have existed throughout the whole history of human society. Before we start to learn more about poker we would like to formulate the general classification of games and to identify the place of poker within its frames. Mostly classifications are relative but still we need them in order to have the general idea of any phenomenon.Athletic games, intellectual games and gambling.Athletic games: the idea of the game, where the final result (victory or defeat) is achieved largely at the expense of athletic qualities of the competitors.Intellectual games: the idea of the game, where the final result (victory or defeat) is achieved largely at the expense of intellectual qualities of the competitors.The relativity of these definitions is obvious. Athletic games (boxing, football or any other type) surely contain intellectual component. In every type of games we have to think. The majority of famous athletes today prefer to keep their personal athletic diaries where they describe in every detail all of their competition and training matters.Standing apart from others is the third type of games: gambling and casino games.The definition of gambling and casino games based on the idea of the game, where the final result (victory or defeat) is achieved by chance. In such kinds of games the athletic or intellectual or any others qualities of the competitors are not principal. Believe it or not but according to this classification poker belongs to the second category, intellectual games. Let’s turn to the more detailed review of the latter.Intellectual games. Games with almost perfect information and games with inexact information.Games with almost perfect information: the idea of the game where all the game information (the position, the players’ actions) is fully open to all participants of the game.To tell the truth there is restricted information even in that kind of games. That is: every player has its own idea of the game action and these thoughts as a rule are unknown to others. Chess is the most striking example of intellectual games with almost perfect information.Games with inexact information: the idea of the game, where the part of information is mutually hidden from all its participants. The information type can be different. For example in backgammon the game position and players’ actions are fully open, however, the result of future dice toss is unknown to all of participants. In turn, in poker the scope of hidden information is bigger: the unknown information is not only the future coming out of cards from a pack but also the cards of each participant because they are hidden from the rest participants of the game.We have made this preliminary analysis in order to draw the readers’ attention to the comparison of two types of intellectual games. As an example for a game with almost perfect information we will examine chess, as this game is probably well-known to our readers. As an example of games with inexact information we will study poker.We have found out that in both the games the final result is achieved by intellectual qualities. But the intellectual effort is just a verbal definition. What does it stand for?