An audit consists of a methodical review and objective examination of an enterprise's financial statements.  The objective of the auditor's examination is to express an opinion on the financial statements, usually in the form of an audit report, which states whether or not the financial information is fairly presented in accordance with Generally Accepted Accounting Principles (GAAP).

For-profit companies generally need audits to comply with a lender's debt covenants, SEC regulations, or various contractual arrangements.  Non-profit organizations often require audits to comply with their granting agreements or board of directors requirements.

How would an audit benefit me?

The auditor's report gives credibility to the financial statements.  The auditors are independent of management and can give an objective opinion on a company's financial statement without bias.