A node is a device or data point in a larger network.
A node can be a couple of different things depending on whether the conversation is about computer science or networking.
In networking a node is either a connection point, a redistribution point, or a communication endpoint. In computer science, nodes are devices or data points on a large network, devices such a PC, phone, or printer are considers nodes.
In general, a node has a programmed or engineered capability that enables it to recognise, process, or forward transmissions to other nodes.