DNS and domains
Registry, registrar, registrant
The three parties behind every domain: the registry runs the extension, the registrar sells the names, the registrant holds one.
The registry operates a top-level domain and its nameservers: DNS-LU for .lu, DNS Belgium for .be, EURid for .eu, Verisign for .com. It sets the rules and the wholesale price, and it does not sell to the public.
The registrar is accredited by the registry to register names on behalf of customers; NovaNode is one. It submits the registration, holds the contact data, collects the fee, and gives you the panel where you set nameservers and renew. Moving a domain between registrars is a transfer; the registry stays the same.
The registrant is the holder, the person or company the domain is registered to, with the rights that come with it: to renew, to transfer, to change nameservers. Whoever is listed as registrant owns the name, whichever registrar it sits with, which is why the contact details on a domain should always be yours and current.