Macs are famously easy to use, one example is deleting applications. Deleting an application is as simple as dragging the App from your Applications folder to the trash. And it works, but this is not always a thorough way of completely deleting an app. Many apps also save your preferences and other data outside of the Applications folder, which do not get deleted when you drag the App to trash.
This is where AppCleaner comes in, it’s a free application that is dead simple to use. When deleting an application, instead of dragging the app into trash, drag it onto AppCleaner and it will locate all the files associated with the app. Hit the delete button, and all those files are moved to Trash.
This ensures that no traces of the application are left on your hard drive that is what we want, unless you plan to reinstall the application later and want to keep your settings.