Any active domain name which is added in a hosting account has a variety of records that permit it to perform properly. In the common case, the name servers (NS records) show the location where the domain name is hosted and they are set on the side of the registrar company, but on the lower level there are specific records set through the hosting company like A (IP address of the website/server), MX (e-mail server), SRV (using a domain name for non-website purposes on a certain port number such as Voice-over-IP), and so on. By having access to these records and by being in a position to edit them, you could have your website with company A and your e-mail messages with company B, for instance. This gives you more freedom as you can choose the best provider for each 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 since some companies have an extra fee for this function.