A node is simply a computer that participates in a network. The term isn’t exclusive to computers and digital networks. An ant is a node in a colony. A human is a node in a society. When talking about cryptocurrencies, there are three main types of nodes. A Light Client keeps a shadow copy of the blockchain, a Full Node stores the entire blockchain and the code base locally, and a Miner verifies the transactions and adds them to the blockchain. Altcoins have all kinds of variations of nodes and proof of stake is ushering in delegates, proposers and other network actors which are all degrees of nodes.