Each and every domain name that is registered and hosted has a great deal 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 address is its IP address i.e. this record shows 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 name for unconventional purposes, including a Voice-over-IP service. To be able to set up and modify particular records allows you to have different services with different companies if, for example, your present host provides good web hosting, but has problems with the email service, or you simply prefer to get a particular service from a particular company. While you will be able to create and modify these records freely and without any restrictions as you own a given domain address, many companies charge extra to give you this option.