It identifies which process is locking a file and gives you the option to kill the process or "unlock" the handle.
If you are trying to delete a file that Windows won't let you touch, you don't necessarily need an "Unlocker.rar": Unlocker.rar
Be extremely cautious when downloading any file named Unlocker.rar from unofficial sources. It identifies which process is locking a file
To help you more specifically, could you tell me or what you are trying to achieve (e.g., deleting a stubborn file or opening a password-protected one)? Unlocker.rar