An "audit", when done properly as an indepenent review, means using multiple pieces of information and matching them up to make sure the pieces measure equally, and if they don't, working out why not.
Audits are often carried out to see if a law or regulation was complied with. Audits check to see if benchmarks, protocols or other standards have been adhered to. Auditors may reveal fraud, waste and incompetence. Audits use useful in proving accountability, integrity and developing trust.