Every single domain name which is registered and hosted has lots of DNS records - some of them are created automatically when you host a domain, others can be created by hand if required. For instance, the A record of a domain is its IP address i.e. this record reveals where the web site is located; the MX records show where the emails are handled, while using an SRV record you can use a domain for unconventional purposes, for instance a Voice-over-IP service. Being able to create and modify specific records permits you to have different services with different providers if, for example, your present host provides stable web hosting, but has difficulties with the e-mail service, or you simply prefer to get a specific service from a certain company. Even though you must be able to set up and edit these records freely and without any limitations as you own a given domain, lots of companies charge extra to give you this option.