Each 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 created manually if needed. For example, the A record of a domain address is its IP address i.e. this record shows where the web site is located; the MX records reveal where the emails are handled, while with an SRV record you can use a domain address for unconventional purposes, for instance a Voice-over-IP service. The ability to create and modify specific records allows you to have different services with different companies if, for example, your current host provides good web hosting, but has problems with the e-mail service, or you simply prefer to get a specific service from a certain company. Though you can create and edit these records freely and with no restrictions as you own a given domain name, many companies charge extra to give you this option.