Every single domain name which 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 needed. As an illustration, the A record of a domain name is its IP address i.e. this record shows where the web site is situated; the MX records reveal where the emails are handled, 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 specific records allows you to have different services with different providers if, for instance, your present host provides good web hosting, but has problems with the e-mail service, or you simply prefer to get a certain service from a particular company. Though you will be able to create and edit these records freely and with no restrictions as you own a given domain name, a lot of companies charge extra to give you this option.