Each domain name that is 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 needed. As an illustration, the A record of a domain address is its IP address i.e. this record reveals where the website is located; the MX records show where the e-mails are stored, 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 particular records permits you to have different services with different companies if, for instance, your present host provides good web hosting, but has issues with the e-mail service, or you simply prefer to get a particular service from a particular company. Although you can set up and edit these records freely and without any limits as you own a given domain address, some companies charge extra to give you this option.