GAAP means Generally accepted accounting principles. The rules governing financial reporting and accounting differ from country to country. US follows GAAP setup by FASB.  IFRS is set up by IASB which specifies exactly how accountants must maintain and report their accounts. Since the advent of globalization, IFRS was established in order to have a common accounting language across the countries, so business and accounts can be understood from company to company and country to country.