INI files are simple text files used for configuration settings in software applications. They typically have a ".ini" file extension and consist of sections, properties, and values. Each section is marked by a header in square brackets, while properties and their corresponding values are listed in key-value pairs. These files are easy to read and edit, making them user-friendly for both developers and users. INI files are commonly used in Windows applications to store settings like user preferences, system configurations, and application options, allowing programs to load these settings at startup.