Any active domain name that is added in a hosting account features a number of records which allow it to function properly. In the typical 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 particular records set through the hosting company such as A (IP address of the website/server), MX (email server), SRV (employing a domain name for non-website purposes on a specific port number like Voice-over-IP), and many others. With access to these records and by being able to modify them, you could have your website with company A and your e-mails with company B, for instance. This offers you more flexibility because you can choose the best provider for each of these services and you don't have to stick with a single company. After you pick a hosting company, you have to make certain that you have access to all DNS records freely as some providers have an extra fee for this function.