Every single domain name which is registered and hosted has a great deal of DNS records - some of them are set up automatically when you host a domain, others can be created by hand if needed. For example, the A record of a domain is its IP address i.e. this record shows where the website is situated; the MX records reveal where the emails are handled, while through an SRV record you can use a domain name for unconventional purposes, such as a Voice-over-IP service. Being able to create and modify particular records allows you to have different services with different companies if, for example, your present host provides good web hosting, but has problems with the email service, or you simply prefer to get a specific service from a particular company. Even though you will be able to set up and modify these records freely and with no limits as you own a given domain address, many companies charge extra to give you this option.