Every domain name that's registered and hosted has a lot of DNS records - some of them are created automatically when you host a domain, others can be set up by hand if needed. As an illustration, the A record of a domain is its IP address i.e. this record reveals where the web site is situated; the MX records reveal where the emails are stored, while using an SRV record you can use a domain for unconventional purposes, like a Voice-over-IP service. The ability to create and modify certain records enables you to have different services with different companies if, for example, your present host provides dependable web hosting, but has issues with the email service, or you simply prefer to get a specific service from a particular company. While you should be able to set up and modify these records freely and with no limits as you own a given domain, a lot of companies charge extra to give you this option.