Any active domain that is added in a hosting account has a number of records which allow it to function properly. In the standard case, the name servers (NS records) show where the domain is hosted and they're set on the side of the registrar company, but on the lower level there are particular records created through the hosting company such as A (IP address of the website/server), MX (e mail server), SRV (using an Internet domain for non-website purposes on a particular port number such as Voice-over-IP), and so on. With access to these records and by having the ability to edit them, you may have your website 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 have to stick with a single company. After you pick a hosting company, you have to make sure that you can access all DNS records freely as some providers have an additional fee for this feature.