What is a node in a blockchain network?
Answer
A node is any computer participating in the blockchain network. Types of nodes: (1) Full node — downloads and stores the entire blockchain history, independently validates all transactions and blocks against consensus rules. Provides maximum security and contributes to network decentralization; (2) Light node (SPV) — downloads only block headers (not full blocks), relies on full nodes for transaction verification. Used in mobile wallets for efficiency; (3) Archive node — stores the full blockchain plus all historical states at every block (needed for querying old state); extremely storage-intensive; (4) Mining/Validator node — participates in block creation (PoW: mining; PoS: staking and validating); (5) Bootstrap node — helps new nodes discover peers. Nodes communicate via a peer-to-peer protocol (like libp2p), gossipping new transactions and blocks. The number of full nodes (Ethereum: ~8,000+; Bitcoin: ~15,000+) directly determines a network's decentralization and censorship resistance.