Every domain name 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 created manually if required. As an illustration, the A record of a domain name is its IP address i.e. this record reveals where the website is situated; the MX records show where the emails are stored, while using an SRV record you can use a domain for unconventional purposes, such as a Voice-over-IP service. To be able to create and modify specific records allows you to have different services with different providers if, for illustration, your present host provides good web hosting, but has issues with the email service, or you simply prefer to get a certain service from a specific company. While you will be able to create and modify these records freely and without any restrictions as you own a given domain, a lot of companies charge extra to give you this option.