Account Abstraction (ERC-4337) transforms Ethereum user experience by decoupling accounts from private keys. It enables smart contract wallets with features like social recovery, gas sponsorship, and batch transactions. This guide explains the technical shift from Externally Owned Accounts (EOAs) to smart accounts, detailing how ERC-4337 works, its benefits for developers and users, and its potential to onboard millions through familiar Web2-like interactions.