An INI file is a simple text file used for configuration settings in software applications. It typically contains sections, properties, and values, allowing programs to read and write settings easily. The structure usually includes a header with section names enclosed in square brackets, followed by key-value pairs. These files are commonly used in various operating systems, including Windows, to store user preferences and application settings. Their straightforward format makes them easy to edit with any text editor, making them accessible for both developers and users who want to customize their software experience.