Most Windows applications will create and place some temporary files on your computer when they are running. When an application terminates, these obsolete files are supposed to be eliminated. However often times they remain on your computer for various reasons such as program errors, sloppy architecture or improper system shutdown.

Many applications also add folders and shortcuts to your Desktop and Start menu during their installation process. This poses no real threat to your system but when you remove a program by deleting it in the program directory, these files are often overlooked.

Junk files refer to these obsolete temporary files, folders and invalid shortcuts, which are useless, yet occupy much disk space, and as a result affect system performance.