A "node" is a fundamental unit in various fields, including computer science, networking, and biology. In computer networks, a node refers to any device that can send, receive, or forward data, such as a computer, printer, or router. Each node has a unique address, allowing it to communicate with other nodes in the network. In the context of data structures, a node is an element that contains data and may link to other nodes. For example, in a linked list, each node holds a value and a reference to the next node, enabling efficient data organization and retrieval.