All three terms refer to the three key entities in operating a domain name.
A domain name registry is a database of all domain names and their information which is controlled and made available by the registry operator. In the UK for example all .uk domain names are governed by Nominet. Whilst some registries also act as a registrar and allow the direct registration of a domain name, this is typically done by a registrar. Additionally a registry will usually hold all the information of the owners of a domain.
A domain name registrar is a company, such as AllThe.Domains, which facilitates the registration of a domain name and acts as an intermediary between the registry making the domain name available and the registrant who has chosen to register it. In some cases both registry and registrar can be the same, however, typically a registrar would be a commercial company. A registrar will be accredited with the registry and follow all its guidelines.
A registrant is the person or entity which has chosen to register a domain name with a registrar. This could be you! Once the order process is completed and it's been accepted by the registry you will officially be the registrant of the domain name and can then choose to have a website or your custom email address. Please note that a small number of domain names will require additional information, such as .ie which requires evidence of a connection to Ireland. Our order process and friendly staff will help guide you through this process.