In professional football, a transfer is the action taken whenever a player under contract moves between clubs. It refers to the transferring of a player's registration from one association football club to another. In general, the players can only be transferred during a transfer window and according to the rules set by a governing body. Usually some sort of compensation is paid for the player's rights, which is known as a transfer fee. When a player moves from one club to another, their old contract is terminated and they negotiate a new one with the club they are moving to, unlike in American, Canadian and Australian sports, where teams essentially trade existing player contracts. In some cases, however, transfers can function in a similar manner to player trades, as teams can offer another player on their squad as part of the compensation.