This is a promise by a Lawyer to ensure that certain conditions (usually of the lender) are met (usually after closing, due to time constraints). The best example is the undertaking to register a discharge of an old first mortgage after the new one has been registered, because there is simply not enough time to do so at closing. It also governs such closing dynamics as releasing funds before a new mortgage document is officially registered.

The process of deciding whether or not to lend you money (or how much to lend you) based on all the information you have given the lender. Every lender has a different underwriting process and lending criteria which differ to some (usually small) extent from other lenders.