Before every tournament, a player has to either play for play-money, freeroll or real money.
In case of play money poker game the player purchases play money credits and in case the player wins the game, he gets the credits back.
In a freeroll tournament, there is no need to buy real money but instead the prize pool is given to the winner which is either in Dollars, Euros or British Pounds. This is ideal for beginners to online poker, as there is no initial investment and still a chance to win some in the end. Some freeroll games are for free where you just need to sign up, some are for frequent player points (FPP). These points are used to buy more credits in future. In other freeroll games, you can get FPP even through play money games.
In a real money game, there is real currency involved. The amount has to be deposited in an account before you buy in. However before starting any real money game, ensure you are using a legal gambling site and from a country that allows online gambling games. Before you do anything on a real money site, find out the procedure to make deposits, withdrawals and make a general enquiry online about the particular’s reputation and financial security.