Each domain which is registered and hosted has lots of DNS records - some of them are created automatically when you host a domain, others can be created by hand if required. For instance, the A record of a domain address is its IP address i.e. this record reveals where the web site is situated; the MX records reveal where the e-mails are handled, while through an SRV record you can use a domain address for unconventional purposes, for instance a Voice-over-IP service. Being able to set up and modify particular records permits you to have different services with different companies if, for illustration, your present host provides dependable web hosting, but has troubles with the email service, or you simply prefer to get a specific service from a specific company. While you will be able to set up and modify these records freely and with no limits as you own a given domain address, some companies charge extra to give you this option.