Node-RED is a programming tool for wiring together hardware devices, APIs, and online services using basic logic flows. It provides a browser-based editor that makes it easy to link together "nodes" that perform actions like connecting to sensors, transforming data, and triggering webhooks. While not intended for large-scale production applications, Node-RED is well-suited for prototyping IoT solutions and integrating different data sources through simple visual programming. It uses JavaScript and runs on Node.js, allowing it to be deployed on devices like Raspberry Pis for connecting physical devices to the cloud.