Most gambling sites, including online poker rooms, make their money by taking a small percentage of each pot as rake. In addition to this, they may also charge entry fees for tournaments, or offer other forms of gaming such as casino games and sports betting.
Some poker rooms also generate revenue by selling virtual goods, such as avatar clothing and accessories, or by offering premium memberships that offer additional features and benefits.
While rake and other fees are the primary source of revenue for online poker sites, they also earn income from advertising. Many poker rooms display advertising from online casinos, sportsbooks, and other gambling-related brands on their websites and in their software client. This can be a significant source of revenue for the poker room, and helps to offset the costs of running the business.
In recent years, some online poker rooms have also begun offering "rake-free" games, where players are not charged any rake or fees. These games are typically supported by advertising or donations from players, and can be a great way to save money on poker.
Some sites also use their online poker purely as a side line to their main business, using it as a loss leader to bring in players who may also spend money on other products such as sports betting or casino games. This can be a very effective marketing strategy, and can result in significant profits for the poker room.