Every domain name which is registered and hosted has quite a lot of DNS records - some of them are created automatically when you host a domain, others can be created manually if required. For example, the A record of a domain is its IP address i.e. this record shows where the website is located; the MX records reveal where the emails are stored, while with an SRV record you can use a domain name for unconventional purposes, like a Voice-over-IP service. Being able to set up and modify particular records enables you to have different services with different companies if, for instance, your present host provides stable web hosting, but has difficulties with the e-mail service, or you simply prefer to get a certain service from a certain company. Although you must be able to 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.