Any active domain name that's added in a hosting account has a number of records that permit it to perform properly. In the standard case, the name servers (NS records) show 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 address for non-website purposes on a specific port number like Voice-over-IP), and many others. Having access to these records and by having the ability to edit them, you can have your website with company A and your e-mail messages with company B, for example. This gives you more freedom since you can choose the best provider for each of these services and you don't need to stick to one company. When you pick a hosting company, you have to make sure that you can access all DNS records freely because some companies have an additional fee for this feature.