Every host on your network that uses the Internet or that can be reached from the Internet should have a name. Each resource record has a hostname field.
Some simple rules are required for hostnames for conformance to accepted Internet standards. Hostnames are called labels and can have alphabetic and numeric characters. A hyphen is allowed if it separates two character strings. Labels might not be all numbers, but they can have a leading digit. Labels must begin and end only with a letter or digit.