A node in a network is a device in a blockchain network that takes responsibility for supporting a network by maintaining a copy of the blockchain and, in some cases, processing transactions. By being distributed across many nodes, a network becomes decentralized.
A node can be any active electronic device, including a computer, telephone, or even a printer, as long as it is connected to the Internet and as such has an IP address. Nodes are often arranged in a structure called binary trees. Each cryptocurrency has its own nodes that maintain the transaction records of that particular token.
As node owners willingly contribute their computing resources to store and validate transactions, they have the ability to collect transaction fees and, on certain networks, earn rewards in the underlying cryptocurrency.