Each domain 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 manually if needed. For instance, the A record of a domain is its IP address i.e. this record reveals where the web site is located; the MX records reveal where the e-mails are stored, while through an SRV record you can use a domain for unconventional purposes, such as a Voice-over-IP service. The ability to set up and modify particular records allows you to have different services with different companies if, for illustration, your current host provides dependable web hosting, but has troubles with the e-mail service, or you simply prefer to get a particular service from a specific company. Even though you must be able to create and modify these records freely and with no limitations as you own a given domain name, lots of companies charge extra to give you this option.