Every domain which is registered and hosted has lots of DNS records - some of them are created automatically when you host a domain, others can be set up by hand if necessary. For example, the A record of a domain 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 using an SRV record you can use a domain address for unconventional purposes, such as a Voice-over-IP service. The ability to create and modify particular records permits you to have different services with different providers if, for illustration, your current host provides good web hosting, but has troubles with the e-mail service, or you simply prefer to get a specific service from a particular company. Although you must be able to set up and edit these records freely and with no limits as you own a given domain name, lots of companies charge extra to give you this option.