NAICS stands for North American Industry Classification System, and it is a standardized system used by government agencies to classify and track businesses in the United States, Canada, and Mexico. One important use of NAICS codes is in list building for targeted marketing efforts. By identifying a business's specific NAICS code, you can ensure that your marketing materials are reaching the right audience.

The North American Industry Classification System (NAICS) is used to classify business establishments by type of economic activity in the United States, Canada, and Mexico. There are five different levels of NAICS codes, which are as follows:

1. Sector: The highest level of NAICS classification, sectors represent broad categories of economic activity. There are 20 sectors in total, which are further divided into 3-digit industry groups.

2. Industry Group: Industry groups are more specific than sectors, and are made up of 4-digit industries. There are a total of 100 industry groups within the NAICS system.

3. Industry: Industries represent the most specific level of NAICS classification, and are made up of 5-digit industries. There are a total of 1,170 industries within the NAICS system.

4. Sub-industry: Sub-industries are even more specific than industries, and are made up of 6-digit sub-industries. There are a total of 11,743 sub-industries within the NAICS system.

5. Product Line: The product line is the most detailed level of NAICS classification, and is made up of 7-digit product lines. There are a total of 117,430 product lines within the NAICS system.