Any active domain that is added in a hosting account includes a variety of records that permit it to work properly. In the general case, the name servers (NS records) show the location where the domain is hosted and they are set on the side of the registrar company, but on the lower level there are particular records set through the hosting company such as A (IP address of the website/server), MX (e-mail server), SRV (employing a domain for non-website purposes on a specific port number like Voice-over-IP), and many others. Having access to these records and by being in a position to modify them, you may have your website with company A and your emails with company B, for example. This gives you more overall flexibility because you can pick the best provider for every one of these services and you do not have to stick to a single company. As soon as you choose a hosting company, you have to make certain that you have access to all DNS records freely as some providers have an additional fee for this function.