Every single domain name which is registered and hosted has lots of DNS records - some of them are created automatically when you host a domain, others can be set up by hand if required. For example, the A record of a domain address is its IP address i.e. this record reveals where the website is situated; the MX records reveal where the e-mails are handled, while through an SRV record you can use a domain name for unconventional purposes, for instance a Voice-over-IP service. The ability to set up and modify particular records allows you to have different services with different providers if, for example, your present host provides good web hosting, but has issues with the email service, or you simply prefer to get a certain service from a certain company. Though you can create and edit these records freely and with no restrictions as you own a given domain name, some companies charge extra to give you this option.