Each and every domain which is registered and hosted has a great deal of DNS records - some of them are created automatically when you host a domain, others can be created by hand if required. As an example, the A record of a domain is its IP address i.e. this record reveals where the web site is situated; the MX records show where the emails are stored, while using an SRV record you can use a domain address for unconventional purposes, including a Voice-over-IP service. The ability to set up and modify certain records enables you to have different services with different companies if, for example, your current host provides good web hosting, but has difficulties with the e-mail service, or you simply prefer to get a specific service from a certain company. While you will be able to create and modify these records freely and without any limits as you own a given domain name, a lot of companies charge extra to give you this option.