The prefix, "pre-" gives it away.
A letter of "preapproval," simply states that you haven't been approved yet, but the lender things you may be.
"Pre-qualification" means that someone has asked a few cursory questions to see if you have a chance of actually being Qualified for a loan. It's like going out on a date - a prequal question might be, "Are you married? Seeing someone?" That doesn't qualify you, it simply "pre" qualifies you.
Final approval isn't just about the borrower, it's about the property, too. The borrower must Qualify - meet all of the requirements; and so must the Property.