Any active domain which is added in a hosting account has a number of records that permit it to work properly. In the standard case, the name servers (NS records) show the location where the domain name is hosted and they are set on the side of the registrar company, but on the lower level there are specific records created through the hosting company like 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), and so on. With access to these records and by having the ability to modify them, you can have your website with company A and your e-mail messages with company B, for illustration. This gives you more flexibility as you can select the best provider for every single one of these services and you do not have to stick to one 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.