The Domain Name System (DNS) is the protocol computer networks use to identify domain names and translate them into Internet Protocol (IP) addresses.
For example, DNS turns a user-friendly domain name, like returnpath.com, into a corresponding IP address, such as 74.125.196.26. It works in the same way that a phone book maps names to phone numbers.
DNS also stores other information, such as a list of mail exchange servers that accept email for a given domain and authentication text such as for a Sender Policy Framework (SPF) record.
Email Glossary