Any active domain name that is added in a hosting account has a variety of records that enable it to perform properly. In the typical case, the name servers (NS records) show where the domain name is hosted and they're set on the side of the registrar company, but on the lower level there are particular records set through the hosting company like A (IP address of the website/server), MX (email server), SRV (using a domain name for non-website purposes on a specific port number such as Voice-over-IP), and many others. Having access to these records and by having the ability to edit them, you could have your web site with company A and your e-mail messages with company B, for illustration. This gives you more independence as you can pick the best provider for every single one of these services and you don't have to stick to a single company. Whenever you choose a hosting company, you have to make sure that you can access all DNS records freely because some providers have an extra fee for this feature.