Every domain that is registered and hosted has a great deal of DNS records - some of them are set up automatically when you host a domain, others can be set up by hand if needed. For instance, the A record of a domain address is its IP address i.e. this record reveals where the website is located; the MX records show where the e-mails are handled, while with an SRV record you can use a domain name for unconventional purposes, like a Voice-over-IP service. Being able to create and modify certain records enables you to have different services with different companies if, for instance, your current host provides good web hosting, but has issues with the e-mail service, or you simply prefer to get a specific service from a particular company. Though you can set up and modify these records freely and with no limits as you own a given domain address, some companies charge extra to give you this option.