Any active domain that's added in a hosting account includes a variety of records which allow it to work properly. In the general case, the name servers (NS records) show the location 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 (email server), SRV (employing an Internet domain for non-website purposes on a particular port number such as Voice-over-IP), and so on. Having access to these records and by being able to edit them, you may have your site with company A and your e-mails with company B, for instance. This gives you more independence because you can select the best provider for each of these services and you don't need to stick with one company. After you choose a hosting company, you have to make certain that you have access to all DNS records freely since some providers have an extra fee for this function.