Any active domain name which 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 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 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 like Voice-over-IP), and so on. Having access to these records and by having the capacity to modify them, you may have your site with company A and your emails with company B, for example. This offers you more freedom since you can pick the best provider for every one of these services and you do not have to stick with a single company. After you select 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 function.