Any active domain which is added in a hosting account has a number of records that enable it to perform properly. In the common 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 particular records created through the hosting company like A (IP address of the website/server), MX (e mail server), SRV (employing a domain name for non-website purposes on a specific port number such as Voice-over-IP), and many others. With access to these records and by having the capacity to edit them, you may have your site with company A and your emails with company B, for example. This gives you more freedom as you can choose the best provider for every one of these services and you don't need to stick with only one company. Whenever you select a hosting company, you have to make certain that you can access all DNS records freely as some providers have an extra fee for this function.