You would need to check out the White Paper for Maker DAO as it has a lot of complexity to it to briefly explain it. https://makerdao.com/

Ethereum has a lot of stuff going on like 0x exchange that allow anyone to trade anything, for any amount, to anyone. You could trade an item from one game for an item in a completely different game for example, or trade ETH for an in game item(for now it has to be ERC20, ERC720, ERC721 on the ETH chain). All free and done via smart contracts through a decentralized system. Places like 0x https://www.0xproject.com/portal They are the step forward for having completely decentralized exchanges on everything, and no fees.