Some technical jargon explained...
The information below should not be taken and used independently but rather as a suppliment. I would always recommend checking this information with a WebMaster or design company before making any decisions.
The registrar is normally the company that the domain name was registered with. Some you may know of are GoDaddy, 1-2-3-Reg and others such as 1and1. These companies maintain the registrant's record.
Typically the individual, business or entity that the domain is registered to. Normally this will be the client. We generally register the domains to ourselves and then update the record for the client once the website is designed but this is by far the most important element of the registration of the domain. If the domain is not registered to you you cannot administer it, change the registrar or request information.
If you find yourself in the position of not being the registrant for your domain and are unable to contact your web designer then we would recommend you secure the services of a WebMaster or designer to help with this.
Normally this will be the WebMaster or web designer. This individual will also be responsible for transferring the domain in or out of a hosting company.
The name servers are where the domain is hosted. This is where the physical website is. It may or may not be the registrar so always try and make sure you know this before making contact with who you might think is the host.
We have a number of clients whose domain name is registered with one company and website is hosted with another.