The National Motor Freight Classification (NMFC) is a standard used to classify commodities for interstate and foreign trade, categorizing them into 18 classes based on characteristics like density, stowability, handling ease, and liability. Correctly determining freight class is essential for tariff calculations and avoiding additional costs, requiring accurate measurements and descriptions of the cargo. For logistics support, shippers can refer to nmfta.org for classifications and should include relevant NMFC codes on the bill of lading when requesting a freight quote.