I'm not 100% sure what you mean by this, but I'm going to take an educated guess. Pinning an app probably means locking it in place on the homescreen so you can't easily move it around or delete it accidentally. Unpinning, probably frees it up for moving and deleting. Neither action would actually delete the app from the phone for that you probably need to go in to Settings, then Apps, then the App, THEN click Uninstall. That actually removes the app and clears space.