Every domain name that's registered and hosted has a lot of DNS records - some of them are set up automatically when you host a domain, others can be created by hand if required. For instance, the A record of a domain is its IP address i.e. this record shows where the site is situated; the MX records show where the e-mails are stored, while with an SRV record you can use a domain for unconventional purposes, like a Voice-over-IP service. The ability to create and modify specific records permits you to have different services with different providers if, for example, your present host provides dependable web hosting, but has issues with the email service, or you simply prefer to get a specific service from a particular company. Even though you should be able to set up and edit these records freely and with no restrictions as you own a given domain, some companies charge extra to give you this option.