What does it mean to revalue a long-term asset? How do U.S. GAAP and IFRS differ regarding

Question:

What does it mean to revalue a long-term asset? How do U.S. and IFRS differ regarding revaluation of long-term assets?
GAAP
Generally Accepted Accounting Principles (GAAP) is the accounting standard adopted by the U.S. Securities and Exchange Commission (SEC). While the SEC previously stated that it intends to move from U.S. GAAP to the International Financial Reporting Standards (IFRS), the...