Pre-approval, as opposed to pre-qualification, signifies that the loan application has been taken through a rigorous procedure. Here's why pre-approved buyers are ahead in the home buying game:
If you make an offer on a home and then apply for a loan, you are at the lender’s mercy, who is aware that you do not have time to shop around.
Pre-approval saves time spent looking at houses you can’t afford.
A pre-approval letter from a lender gives you an edge when multiple offers have been made on a house.
Pre-approved buyers can generally close escrow more quickly, since most of the work has already been done.