A Custom ROM is a modified version of the operating system for mobile devices, particularly those running on the Android platform. Unlike the standard firmware provided by manufacturers, Custom ROMs offer users enhanced features, improved performance, and the ability to personalize their devices. They are created by independent developers and can provide updates even after the official support has ended. Installing a Custom ROM typically requires unlocking the device's bootloader and using a custom recovery tool. Popular examples of Custom ROMs include LineageOS and Pixel Experience. Users often choose Custom ROMs to gain access to the latest Android features or to remove bloatware that comes with stock versions.