App Uninstaller is a special app designed to delete other apps. If you simply drag any application to the Trash some files may left. Have you wondered that if you uninstall and after a while install any messenger again you have older message history? You may guess it’s because they are saved online? No, they are saved on your hard drive!
When you dragged app to the Trash, you simply deleted .dmg file when all service files left on your hard drive. See real structures of messenger applications:
Some messengers’ service files may store huge amount of space. You can delete them with your own hands or give this task to App Uninstaller. The app is also great if you need to refresh any app. Simply delete all files except .dmg.