Each and every domain that is registered and hosted has quite a lot of DNS records - some of them are created automatically when you host a domain, others can be set up manually if needed. As an example, the A record of a domain is its IP address i.e. this record reveals where the website is located; the MX records reveal where the emails are handled, while with an SRV record you can use a domain address for unconventional purposes, including a Voice-over-IP service. The ability to create and modify certain records permits you to have different services with different companies if, for example, your current host provides dependable web hosting, but has problems with the e-mail service, or you simply prefer to get a specific service from a particular company. Though you should be able to create and modify these records freely and with no restrictions as you own a given domain address, a lot of companies charge extra to give you this option.