An audit is an independent evaluation of a process, outcome or report with a view to providing a level of assurance to various stakeholders.
Most commonly audit is referred to as "the provision of assurance over a historical financial report". The audit of financial statements provides an independent opinion on the truth and fairness of financial statements prepared by management. This provides the stakeholders, generally the shareholders or members, with a degree of comfort in relation to the reliability of the financial report.
Audit Guide - An overview of Audit