Layer 2 (L2) is a collective term for off-chain scaling solutions that inherit the security of a Layer 1 blockchain while processing transactions faster and cheaper. Major categories include Optimistic Rollups (Arbitrum, Optimism) and ZK Rollups (StarkNet, zkSync).
Smart contracts are self-executing programs stored on a blockchain that automatically enforce the terms of an agreement when predefined conditions are met. They are the foundation of DeFi, NFTs, and decentralised autonomous organisations.
MetaMask is the world's most popular Ethereum wallet, available as a browser extension and mobile app. It allows users to interact with decentralised applications directly from their browser, store Ethereum and ERC-20 tokens, and sign transactions. With over 30 million monthly active users, it is the primary gateway to Web3.
Solidity is the primary programming language for writing Ethereum smart contracts. It is a statically-typed, contract-oriented language with syntax influenced by JavaScript and C++. It powers virtually all DeFi protocols, NFT contracts, and DAOs on Ethereum and EVM-compatible chains.