Every single domain name that is registered and hosted has a lot of DNS records - some of them are created automatically when you host a domain, others can be created by hand if necessary. For instance, the A record of a domain address is its IP address i.e. this record shows where the site is located; the MX records reveal where the emails are handled, while with an SRV record you can use a domain name for unconventional purposes, such as a Voice-over-IP service. The ability to create and modify particular records allows you to have different services with different companies if, for illustration, your present host provides dependable web hosting, but has issues with the email service, or you simply prefer to get a particular service from a certain company. While you should be able to set up and modify these records freely and with no limits as you own a given domain, some companies charge extra to give you this option.