Protecting backed up files?

This, I am sure, is a stupid question but I want to make sure…

If I delete files on my laptop that are backed up with my WD Passport will they also delete on the backup when I update? I want to clean up my full drive on my laptop (photos, documents, etc.) but I don’t want to lose them, particularly the photos and videos of my grandchildren and some critical documents…

unless you are using a Sinchronization software the files will stay on the drive.

Please note that a backup is having the information in two different places just in case that one fails.