Each and every domain 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 created by hand if necessary. As an illustration, the A record of a domain address is its IP address i.e. this record reveals where the site is situated; the MX records show where the emails are stored, while using an SRV record you can use a domain address for unconventional purposes, such as a Voice-over-IP service. Being able to create and modify particular records permits you to have different services with different providers if, for illustration, your present host provides stable web hosting, but has difficulties with the email service, or you simply prefer to get a particular service from a specific company. Although you should be able to create and edit these records freely and without any limitations as you own a given domain address, lots of companies charge extra to give you this option.