Node

A node is a computer or device that connects to a blockchain network. Each node maintains a copy of the blockchain and validates and relays transactions.
Nodes ensure the integrity and security of the network by verifying new blocks of transactions. They can be full nodes, which store the entire blockchain, or lightweight nodes, which only store part of it.
Essentially, nodes are critical for the decentralized nature of blockchains, allowing the network to operate without a central authority.