The U.S. Census Bureau publishes the official NAICS Manual, and offers a searchable version on its website. You can also download the entire manual in PDF format.
The NAICS Association, a trade organization, provides a database of NAICS codes that can be searched for free.
The North American Industry Classification System (NAICS) is a list that groups similar businesses together and assigns a number to each category. The U.S. government uses these classification codes to organize data collected about various industries.
Some Library databases, such as D&B Hoover's, can be searched by NAICS code, so it may help you to know how businesses in the Hospitality industry are numbered.
Sector 72 = Accommodation & Food Services, so everything listed in this category begins with the digits "72." Here's how the categories look in D&B Hoover's: