In the context of the blockchain, a node refers to every computer running a Bitcoin client. So the Bitcoin network consists of thousands of computer nodes spread all over the world, and this is what makes Bitcoin a peer-to-peer distributed economic system.
Each blockchain node is a communication point in the network. There are several types of nodes, and each type is responsible for performing a different set of functions. Taking Bitcoin as an example, network nodes can be divided into four main groups: full nodes, supernode nodes, miner nodes, and lightweight clients or SPV.
The full node is one that truly supports and secures the Bitcoin blockchain, and they are indispensable for the network. The full node (or node that fully validates) is responsible for verifying transactions and blocking in accordance with the rules of the Bitcoin protocol. And because the network is distributed, the rules are enforced by the Bitcoin consensus algorithm.
Listening nodes, or supernodes, are full nodes that are made publicly accessible and accessible. Thus, they can communicate with other nodes that make connections with them. So any node that fully validates that is not hidden can be considered a hearing node. This type of node is responsible for providing blockchain data to other nodes, but they can also function as communication bridges.
Mining nodes are those that run special mining software, together with ASIC machines (in many cases). They invested a lot of resources hoping to get a bitcoin prize. While the solo miner fully validates the node, the miner’s pool often provides computing resources without downloading the entire blockchain data. So only the pool administrator is needed to run the full node.
Finally, lightweight clients or SPV are those who use the Bitcoin blockchain but do not function as validation nodes. They only collect information from the supernode, acting as a communication endpoint. As such, these nodes do not keep a copy of the blockchain and do not contribute to network security.