Each and every domain that's 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 manually if required. As an illustration, the A record of a domain name is its IP address i.e. this record reveals where the web site is situated; the MX records show where the e-mails are handled, while through an SRV record you can use a domain name for unconventional purposes, for instance a Voice-over-IP service. To be able to create and modify specific records permits you to have different services with different providers if, for instance, your current host provides stable web hosting, but has troubles with the e-mail service, or you simply prefer to get a particular service from a particular company. Though you should be able to create and edit these records freely and with no restrictions as you own a given domain name, many companies charge extra to give you this option.