Smart contracts are autonomous. They are stored on the Ethereum blockchain, therefore, they are immutable. Their execution results are stored on the Ethereum blockchain. Therefore, the execution of Ethereum smart contracts is irreversible. Ethereum. "What Is Ethereum?" Bitcoin was the first blockchain, but Bitcoin was only meant for payments. People started discovering that Bitcoin could be used for other scenarios; we call this Colored Coins. Bitcoin had a surprisingly open design and one guy, Vitalik Buterin, decided to start developing Ethereum on top of the Bitcoin blockchain. But, due to limitations in Bitcoin, Ethereum now has its own blockchain. While Ethereum's performance has been dominating the spotlight, another to see crypto project is garnering significant attention in the freelancing sector.