Mortgage pre-approval
Mortgage pre-approval is when a lender reviews your official loan application, finances and credit, then tells you the specific amount you are approved to borrow and the interest rate. It goes further than pre-qualification.
New Jersey example
A buyer house hunting in Morris County first gets pre-qualified by phone, usually at no cost, which does not include a credit report review. Next they file a mortgage application, pay the fee and get pre-approved for a specific amount. Sellers see they are serious, and they can still take the final loan from a different lender.
Official source
This is a plain-English summary. Rules and dollar amounts change, so check the official source or a professional before you file or sign anything.