IO stands for Input/Output, a fundamental concept in computing that refers to the communication between a computer and the outside world. Input involves receiving data from devices like keyboards, mice, or sensors, while output is the process of sending data to displays, printers, or speakers. This interaction allows users to control and receive information from their devices. In programming, IO operations are essential for reading and writing data. For example, when a program reads a file, it performs an input operation, and when it saves data, it executes an output operation. Efficient IO management is crucial for optimizing performance in software applications.