Each domain name that is registered and hosted has lots of DNS records - some of them are set up automatically when you host a domain, others can be created by hand if needed. As an illustration, the A record of a domain name is its IP address i.e. this record reveals where the web site is located; the MX records show where the emails are managed, while through an SRV record you can use a domain name for unconventional purposes, like a Voice-over-IP service. To be able to set up and modify certain records allows you to have different services with different providers if, for instance, your present host provides dependable web hosting, but has troubles with the email service, or you simply prefer to get a specific service from a specific company. While you must be able to create and edit these records freely and with no limits as you own a given domain address, a lot of companies charge extra to give you this option.