The DNS settings allows you to change the A record, MX record, CNAME and name servers for your domain name.
A record: An A record is part of the zone file. It is used to point Internet traffic to an IP address. For example, you can use an "A record" to designate abc.yourdomain.com to send traffic to your web site at IP address 126.96.36.199. You can also designate xyz.yourdomain.com to go to a separate IP address.
MX Record: Mail Exchange
A Mail Exchange record is part of the zone file and is used to designate which mail server machine should process e-mail for a specific domain.
CNAME: canonical name
Also referred to as a CNAME record. It is a record in a DNS database that indicates the true host name of a computer that its aliases are associated with. For example, if "mail.example.com" points to a mail server instead of the IP address, you could put in "mail.example.com CNAME webmail.other-reg.com" so that if the IP address of the mail server (webmail.other-reg.com) is changed, you won't have to make any updates.
A computer that performs the mapping of easily remembered domain names to IP addresses. Sometimes referred to as a host server.