Every single domain which is registered and hosted has quite a lot of DNS records - some of them are created automatically when you host a domain, others can be set up manually if necessary. As an illustration, the A record of a domain is its IP address i.e. this record shows where the site is situated; the MX records reveal where the emails are handled, while with an SRV record you can use a domain address for unconventional purposes, like a Voice-over-IP service. The ability to set up and modify particular records permits you to have different services with different companies if, for illustration, your present host provides stable web hosting, but has troubles with the e-mail service, or you simply prefer to get a certain service from a certain company. Even though you can create and modify these records freely and without any limitations as you own a given domain, many companies charge extra to give you this option.
