What is a registrar?
A registrar is a unit offering registration of domain name to end users.
The different top level domains are administrated by the different registries, e.g. NORID for .no domains and DK Hostmaster for .dk domains. However, people wanting a domain name cannot normally register it directly through the registry.
Registration and changes must be made via an accredited registrar. The registrar is the connection between the customer (domain name owner) and the registry, also called the top level registrar.