Every domain name that's 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 manually if needed. For example, the A record of a domain name 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 through an SRV record you can use a domain for unconventional purposes, such as a Voice-over-IP service. Being able to set up and modify particular records permits you to have different services with different providers if, for illustration, your present host provides stable web hosting, but has difficulties with the email service, or you simply prefer to get a particular service from a specific company. While you can set up and modify these records freely and with no limits as you own a given domain, some companies charge extra to give you this option.