Any active domain name that's added in a hosting account includes a number of records that permit it to perform properly. In the general case, the name servers (NS records) show where the Internet domain is hosted and they're set on the side of the registrar company, but on the lower level there are certain records set through the hosting company such as A (IP address of the website/server), MX (email server), SRV (employing a domain address for non-website purposes on a certain port number such as Voice-over-IP), and many others. By having access to these records and by being able to edit them, you could have your site with company A and your e-mails with company B, for illustration. This offers you more freedom since you can choose the best provider for every single one of these services and you don't have to stick to one company. Whenever you pick a hosting company, you have to make certain that you have access to all DNS records freely because some providers have an extra fee for this function.