Not sure what's on your computer or how it got there? Disk Cleaner was designed to show you and help you keep your computer running clean.
Having a computer for some time, you forget how many programs you've installed, uninstalled, deleted, the number of files that were copied and so on. Where does all that garbage go? It's still there and Disk Cleaner was designed to help you recover all of the space that it taking up on your hard drives.