Any computer integrated into the blockchain network is a node. Nodes that fully download all blockchain network data are called full nodes. They download every generated block and every transaction, check them against blockchain consensus rules and store the complete blockchain.
Full nodes are the foundation of blockchain security. For the stable functioning of the platform, a network of full nodes is required that constantly work without interruption, ensuring continuous work with the current version of the blockchain.
The more full nodes in the network, the better the decentralization principle is maintained and the better the network is secured, because users can always find a suitable node to record transactions on.