Pre-Qual vs Pre-Approval.
Most people use the term synonymously however there are some major differences.
A Pre-Qual is a conversation between you and the lender. they use the information you provide without checking to come up with a estimate of the amount of home you can afford.
A Pre-approval normally involves the lender pulling a credit bureau confirming your income and debts to determine the amount you can actually afford. There is no possibility of the person being unable to purchase the home due to credit or income issues as all of this has been done beforehand.
Buyers and sellers should want the pre-approval process as the only remaining issue is then an appraisal.