F2P

Free-to-play (F2P) refers to video games which give players access to a significant portion of their content without paying. There are several kinds of free-to-play games, but the most common is based on the freemium software model. For freemium games, users are granted access to a fully functional game, but must pay microtransactions to access additional content. Free-to-play can be contrasted with pay to play, in which payment is required before using a service for the first time.

The model was first popularly used in early massively multiplayer online games targeted towards casual gamers, before finding wider adoption among games released by major video game publishers to combat video game piracy and high system requirements. Without upfront payment, publishers may charge money for in-game items or integrate advertisements into the game.

There are several kinds of free-to-play games:

In-game items can be purely cosmetic, enhance the power of the player, or accelerate progression speed. A common technique used by developers of these games is for the items purchased to have a time limit; after this expires, the item must be repurchased before user can continue. Another commonly seen mechanic is the use of two in-game currencies: one earned through normal gameplay, and another which can be purchased with real-world money. The second, "premium" currency is sometimes given out in small amounts to non-paying players at certain times, such as when they first start the game, or when they complete a quest or refer a friend to the game. Many browser games have an "energy bar" which depletes when the player takes actions. These games then sell items such as coffee or snacks to refill the bar. It is unknown whether energy timers, by imposing break times between game sessions, help players avoid getting addicted to free-to-play games.

...
Wikipedia