DNS records stands for Domain Name Server records. These are the records which tell other servers what IP address is associated with one of your domain names. There are a number of different record types but the most common ones are A-records (Address records) and MX records (mail records).

The address records simply point a domain at an IP address so that when someone types a domain name in their browser, they get the correct website. The MX records point a domain at the mailserver so that any incoming mail on that domain can be forwarded to the correct place.