GAAP stands for Generally Accepted Accounting Principles, which is a set of accounting standards, procedures, and rules that public companies must follow. GAAP is issued by the Financial Accounting Standards Board (FASB). GAAP ensures that all publicly traded companies follow the same accounting reporting standards, which makes it easier for investors to compare the financials of different companies.
Some reporting areas covered by GAAP include revenue recognition, balance sheet classification, and materiality. For publicly traded companies, they must use GAAP reporting as mandated by the U.S. Securities and Exchange Commission (SEC).