SAX, or Simple API for XML, is a programming interface used for parsing XML documents. It allows developers to read and process XML data in a sequential manner, meaning that the parser reads the document from start to finish without loading the entire file into memory. This makes SAX efficient for handling large XML files. In SAX, events are triggered as the parser encounters different parts of the XML structure, such as elements, attributes, and text. Developers can define handlers to respond to these events, enabling them to extract and manipulate data as needed. SAX is commonly used in languages like Java and Python.