Every single domain that's registered and hosted has lots of DNS records - some of them are set up automatically when you host a domain, others can be set up manually if required. As an illustration, the A record of a domain is its IP address i.e. this record reveals where the site is located; the MX records show where the e-mails are managed, while through an SRV record you can use a domain name for unconventional purposes, including a Voice-over-IP service. Being able to set up and modify particular records enables you to have different services with different providers if, for example, your present host provides dependable web hosting, but has problems with the email service, or you simply prefer to get a certain service from a certain company. Although you should be able to create and modify these records freely and without any restrictions as you own a given domain name, lots of companies charge extra to give you this option.