Any active domain which is added in a hosting account includes a variety of records that permit it to perform properly. In the general case, the name servers (NS records) show where the domain name is hosted and they're set on the side of the registrar company, but on the lower level there are certain records created through the hosting company like A (IP address of the website/server), MX (e-mail server), SRV (using a domain for non-website purposes on a specific port number like Voice-over-IP), and so on. Having access to these records and by having the ability to edit them, you may have your website with company A and your e-mail messages with company B, for instance. This offers you more independence because you can choose the best provider for each of these services and you don't need to stick to a single company. After you pick a hosting company, you have to make sure that you have access to all DNS records freely because some companies have an extra fee for this function.