Word of Mouth advertising is a very powerful tool and online casinos acknowledge this power and rely on it for the purpose of attracting new players to the casino.
The way that they do this is by offering their players incentives for referring friends and relatives to the casino.
The main incentive online casinos offer their players in order to get them to promote the casino to their friends and relatives, is the Refer a Friend Bonus.
In most online casinos the Refer a Friend bonus is of a fixed amount that is awarded to a player when someone they have referred to the casino makes their first deposit.
There is usually a minimum sum for the deposit the new referred player needs to make in order for the original player referring them to get the bonus.
Some online casinos limit the number of Refer a Friend bonuses a player can get and others do not place such restrictions and players can continue to collect Refer a Friend bonuses as long as they keep referring new players.
In addition some casinos have a 'two-way street' bonus policy where the referring player will get a bonus but also the referred player will get a bonus from the casino. Most online casinos that offer such a bonus would usually reward the referring player with a higher bonus than the player being referred.