Each domain name that is registered and hosted has a lot of DNS records - some of them are created automatically when you host a domain, others can be created by hand if required. As an example, the A record of a domain is its IP address i.e. this record shows where the website is situated; the MX records reveal where the e-mails 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 set up and modify specific records enables you to have different services with different providers if, for illustration, your current host provides good web hosting, but has difficulties with the email service, or you simply prefer to get a specific service from a certain company. Even though you will be able to set up and edit these records freely and without any restrictions as you own a given domain name, lots of companies charge extra to give you this option.