Along with the premium version, they have a crypto currency (TON) that can be used to buy things on the platform from other users, and I think you can also buy things with real money and they keep a small commission. Also there are some small ads in very large channels (not groups, channels only) and ways to gift “stars” to other people, like Patreon or sth
Oh man, Super Hexagon! So so so many hours on Android a decade ago. Bought it!