Java IO (Input/Output) is a set of classes and interfaces in the Java programming language that enables developers to read from and write to data sources like files, network connections, and memory. It provides a way to handle data streams, allowing for efficient data processing and manipulation. The Java IO framework includes various components, such as File, InputStream, and OutputStream, which facilitate different types of data handling. It supports both byte and character streams, making it versatile for handling binary data and text. This functionality is essential for applications that require data persistence and communication.