Having full control of your domains is something really crucial and being able to access and edit the DNS records for each of them is among the things you should look for when you search for a registration or a shared web hosting provider. Maybe you have heard of the so-called “name servers” that show where a domain address is hosted, but below them there's a whole group of records, for example the A record, which is the IP address of the server hosting the site, and the MX records, which show the server that handles the emails for a particular domain. These records are used if you want to have your site with one provider and the emails with another, for instance. You could also use a domain for a non-website service or forward the traffic to it by using special records. Some companies ask for an additional fee to give access to edit certain DNS records other than the name servers.