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