Smart contracts are a foundational technology in blockchain and a key element of the Ethereum network. A smart contract is self-executing code that carries out a set of instructions, which are then verified on the blockchain. These contracts are trustless, autonomous, decentralized, and transparent; they are irreversible and unmodifiable once deployed. Quite popular in decentralized finance (DeFi), they have several other use cases. Smart contracts can be bundled into decentralized applications (dApps) to execute more complex functions.