Any active domain that is added in a hosting account features a variety of records which allow it to function properly. In the standard case, the name servers (NS records) show the location where the Internet domain is hosted and they are 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 so on. Having access to these records and by having the capacity to edit them, you may have your web site with company A and your emails with company B, for instance. This gives you more overall flexibility because you can choose the best provider for every one of these services and you don't need 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 since some providers have an extra fee for this feature.