DNS is the abbreviation of Domain Name System (and not for Domain Name Server or Domain Name Software) is a system that catalogs domains and the corresponding IP addresses on the internet. The database is stored through a network of servers. The database is maintained and managed by IANA (Internet Assigned Numbers Authority) and ICANN (Internet Corporation for Assigned Names and Numbers).
There are different types of DNS records: NS is the nameserver record; A record is the most important providing the domain’s IP address. MX records provides the IP address of email addresses. TXT records are used for any unique text that usually serves for certification purposes.