Every single domain name that's 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 needed. As an illustration, 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 emails are stored, while through 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 providers if, for example, your present host provides good web hosting, but has issues with the email service, or you simply prefer to get a specific service from a specific company. While you will be able to set up and modify these records freely and with no limits as you own a given domain, many companies charge extra to give you this option.