Definition
A node is a participating instance of network software. Nodes communicate with peers and perform roles such as relaying transactions, checking blocks or answering data requests. Their responsibilities depend on the protocol and node type. Not every node stores all historical data or participates in block production.
Different Roles
A full node independently applies the network’s validity rules. A light client works with less data and uses proofs or other assumptions to check information. An archive configuration may retain historical state for detailed queries. Mining and validator functions are additional roles associated with particular consensus mechanisms; running ordinary node software does not automatically earn block rewards.
Uses and Limitations
Applications rely on nodes to submit transactions and retrieve balances or contract state. Running a suitable node can reduce dependence on a third-party data provider, but it requires maintenance, synchronization and resources. Node count alone is not a complete measure of decentralization: ownership, connectivity, software diversity and practical ability to verify the chain also matter. A service endpoint may represent infrastructure managed by someone else rather than an independently controlled node.