Each domain which is registered and hosted has a lot of DNS records - some of them are set up automatically when you host a domain, others can be created by hand if needed. As an illustration, the A record of a domain address is its IP address i.e. this record shows where the web site is located; the MX records reveal where the emails are managed, while using an SRV record you can use a domain name for unconventional purposes, including a Voice-over-IP service. To be able to create and modify specific records permits you to have different services with different companies if, for illustration, your present host provides dependable web hosting, but has troubles with the e-mail service, or you simply prefer to get a certain service from a particular company. Though you must be able to create and modify these records freely and without any limits as you own a given domain address, lots of companies charge extra to give you this option.