Every domain name that is registered and hosted has a great deal of DNS records - some of them are created automatically when you host a domain, others can be created by hand if needed. For instance, the A record of a domain is its IP address i.e. this record reveals where the site is situated; the MX records show where the emails are stored, while through an SRV record you can use a domain address for unconventional purposes, including a Voice-over-IP service. The ability to set up and modify particular records enables you to have different services with different companies if, for instance, your current host provides stable web hosting, but has difficulties with the email service, or you simply prefer to get a particular service from a particular company. Even though you can set up and modify these records freely and without any limits as you own a given domain address, lots of companies charge extra to give you this option.