The certificates and policy documents proving the borrower carries the property, liability, and specialty coverages the loan documents require, with the lender properly named.
The longer version
Lenders check coverage amounts, deductibles, carrier ratings, and the clauses that protect them: mortgagee and lender's loss payable on property coverage, additional insured on liability. ACORD 28 evidences property; ACORD 25 certificates evidence liability.
Insurance review is detail work that fails late if started late, because fixing a non-compliant policy needs the broker and sometimes the carrier. Renewal tracking then continues for the life of the loan.
In Prodeal
Insurance documents run as checklist lines with statuses and due dates, and the servicing side tracks renewals with reminders routed to the responsible party.