A smartphone cleaner & booster is a mobile application designed to optimize the performance of a smartphone by cleaning up junk files, freeing up storage space, and boosting the device's speed. The app typically scans the phone for unnecessary files, such as cached data, temporary files, and residual files from uninstalled apps, and allows the user to delete them with just a few taps. Additionally, the booster feature can help speed up the phone by stopping unnecessary background processes and freeing up RAM. Overall, a smartphone cleaner and booster can improve the user experience by enhancing the device's speed and freeing up storage space.