Play games
Choose the game that interests you and play itfor free.
Complete the quests
Every game has some quests for which you will receive Soul Gems.
Receive rewards
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
Like the title says, never heard of it. It sounds like WT/WoT, and, as I have a very love/hate relationship with WT right now (1.91 isn't looking to be good), I'm wondering how this game is.