Any active domain name that's added in a hosting account has a variety of records which allow it to perform properly. In the common case, the name servers (NS records) show the location where the Internet domain is hosted and they're set on the side of the registrar company, but on the lower level there are specific records set through the hosting company such as A (IP address of the website/server), MX (e mail server), SRV (employing a domain name for non-website purposes on a particular port number such as Voice-over-IP), etc. By having access to these records and by being in a position to edit them, you may have your site with company A and your e-mails with company B, for instance. This offers you more flexibility because you can select the best provider for every one of these services and you do not have to stick to a single company. As soon as you pick a hosting company, you have to make certain that you can access all DNS records freely since some providers have an additional fee for this function.