Additional means of payment appearing most often in MMO productions distributed on a free-to-play basis. Premium currency (e.g. diamonds, platinum, coins) is sold through the microtransaction system and allows you to purchase special items and amenities unavailable to players using the free game options.
In order to reduce the disproportion between paying and « free » players, in some games there is an opportunity to get small amounts of premium currency while playing. As a rule, however, it requires a lot of time and a certain amount of luck.