particularly what is a mapped network(in this instance)
The user's IP address is referenced, and the series of numbers that make up a user's network address (ex. 18.104.22.168) is noted. These Network addresses are referenced against the DART server's database of more than 400,000 mapped networks.
Each mapped network reveals the user's Domain (att.net, Microsoft.com, etc.), and the following information about that Domain: Country, and in the U.S and Canada -State, Postal Code, Area Code and SIC Code.
Note: Use of the user's IP address allows more targeting than with top-level domain alone (i.e .com). Regional targeting features and SIC code targeting will also be made available in International markets in the future.