The Generally Accepted Auditing Standards (GAAS) are a set of established standards for which all auditing must be measured against. The general characteristics of an auditor under the GAAS is that the auditor must remain unbiased and objective when auditing, they must be qualified and exercise professional care when performing the audit.
The standards of actual field work the auditor must adhere to are planning and supervising all activity regarding the audit (including the supervision of assistants), extensive knowledge regarding the processes of the company that is it auditing (ex. Internal control, financial statements, organizational behaviour, etc.) and the ability to provide accurate evidence concerning any decisions they, or the company, may make regarding the accounting. Lastly, there are standards of reporting in accordance with GAAS. These reporting standards are that the auditor must ensure that the report is in accordance with the Generally Accepted Accounting Principles (GAAP), identify the circumstances in which the principles have been constantly observed, state any concerns the auditor may have regarding the financial reports of a company and, finally, state their opinion regarding the financial statements and provide reasoning for their logic.
It is important for a standard of auditing to exist so that all auditors can adhere to the same principles, in order to create comparable reports.