Any active domain that's added in a hosting account features a variety of records that permit it to function properly. In the general case, the name servers (NS records) show where the Internet domain 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 (email server), SRV (employing a domain address for non-website purposes on a specific port number such as Voice-over-IP), etc. Having access to these records and by having the capacity to modify them, you can have your web site with company A and your e-mail messages with company B, for example. This offers you more freedom because you can choose the best provider for each of these services and you don't need to stick to one company. As soon as you pick a hosting company, you have to make certain that you can access all DNS records freely as some companies have an extra fee for this feature.