A pre-approval is a preliminary approval offered by banks to clients who are looking to obtain property finance but haven’t yet found a property.
The bank can issue a pre-approval based on your maximum eligibility, the loan amount applied for isn’t final but is the maximum which the bank will be able to lend.
Once you have a pre-approval you can be confident of receiving final approval and a mortgage from the bank as long as your circumstances haven’t changed from your initial application.