INI is a simple `key = value` config format with optional `[section]` headers, originally from MS-DOS and Windows 3.x. Still widely used because of its readability — Git, MySQL, PHP, Python's configparser, and countless tools use INI for their configs. No standard spec, so dialects vary: some allow `:` as separator, some support `;` or `#` comments, some allow nested sections with dots in keys.
How to open
Any text editor. Most operating systems associate `.ini` with Notepad/TextEdit by default. Tools that consume INI files load them directly without manual parsing.