Every domain which is registered and hosted has a lot of DNS records - some of them are set up automatically when you host a domain, others can be created manually if required. For example, the A record of a domain address is its IP address i.e. this record reveals where the web site is situated; the MX records reveal where the e-mails are handled, while through an SRV record you can use a domain for unconventional purposes, including a Voice-over-IP service. The ability to set up and modify certain records enables you to have different services with different companies if, for illustration, your present host provides good web hosting, but has problems with the e-mail service, or you simply prefer to get a particular service from a certain company. Though you should be able to set up and edit these records freely and without any restrictions as you own a given domain name, some companies charge extra to give you this option.