GAAP (Generally Accepted Accounting Principles) is a set of accounting rules and standards used in the United States, while GAAS (Generally Accepted Auditing Standards) is a set of auditing standards used by auditors when examining and reporting on financial statements. While GAAP provides guidelines for how financial statements should be prepared, GAAS provides guidelines for how auditors should conduct their audits and issue their reports. In summary, GAAP focuses on accounting principles, while GAAS focuses on auditing standards.