Use this tag when your issue is specific to custom ROMs -- but first make sure that there's no more specific tag, as e.g. for 'cyanogenmod' or 'darky-rom'. See the full tag wiki for more details.
What is a Custom ROM?
A custom-rom is a modified version of Android, often made by a community. They contain improvements and new features over the official firmware releases of the device manufacturers, and often come with a more pure Android experience (no bloatware etc.)