Each domain name which 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 set up by hand if required. As an illustration, 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 e-mails are managed, while using an SRV record you can use a domain name for unconventional purposes, like a Voice-over-IP service. The ability to set up and modify certain records enables you to have different services with different companies if, for illustration, your current host provides stable web hosting, but has troubles with the email service, or you simply prefer to get a particular service from a certain company. Though you will be able to set up and edit these records freely and without any limitations as you own a given domain name, a lot of companies charge extra to give you this option.