Aztec is a privacy-first Layer 2 (L2) solution on Ethereum, leveraging zero-knowledge proofs to enable confidential transactions and smart contract execution. It supports both private and public functions, allowing for composability between private/public execution and state. Aztec introduces a new alt-VM, distinct from the Ethereum Virtual Machine (EVM), to facilitate its privacy features. Developers can utilize tools like Aztec.js and the Noir programming language to build privacy-preserving applications.