What is a domain?
Strictly speaking, it is a name (See domain name below). But in common usage we are often referring to the most basic part of a group of domain names (e.g. baremetal.com being the domain behind the names www.weblinknepal.com and ftp.baremetal.com and http://weblinknepal.com/ ). In this sense it is more like an address (123 some street) for an infinitely expandable house (so you can just keep adding suite numbers
What is a domain name or a fully qualified domain name??
It is a convenient name (or label) for some information that would be awkward to refer to directly. Usually that information is an IP address (which is 4 numbers between 0 and 255, e.g. 192.168.10.250).
What is a domain registration?
A domain registration is a 'right to use' for a given domain. Usually registrations cost money, and are sold by the year.
What is a domain registrant?
A registRANT is the organization that has purchased a domain registration.
What is a domain registrar?
A registRAR is an organization that sells domain registrations. Usually registrars have a contract with a registry, and often are certified by an organization. Some Registrars use resellers (like OpenSRS), so it may be hard to know who the registrar is. Some registrys sell direct, so the registrar and the registry may be the same organization.
What is a domain registry?
A registRY is the single organization that co-ordinates the domain registrations for a given top level domain (e.g. .com, .ca, or .info).
How is a domain registered?
Generally, the organization that wants to register a domain ( which might be an individual), contacts a registrar or visits a registrar's website, requests a particular domain name, provides some contact information, provides some other information (which may include a chosen password, and/or DNS servers, and usually payment information like a credit card number).
The Registrar then sends the appropriate information/request to the registry to complete the registration.
What is a WHOIS record?
For most domains, much of the contact information provided during the registration process is put into a public whois record.
(The .com domains are one extreme, with full info for the registrant, plus admin, technical, and billing contacts. At the other extreme is .co.uk which provides registrant name, the name of the registrar and the DNS servers.)
What are the domain contacts?
They are the people you contact if you have questions about the domain or trouble accessing it.
Just as importantly, the admin contact is the authority allowed to make changes to the domain, and the billing contact (if there is one) is where the domain expiration messages go to.
What are DNS Servers ?
DNS servers are what actually makes a domain name work. By work I mean that they convert a text label to the information like IP addresses that the Internet is based on. (See 'What is a domain name'.)
This is not to say that they handle e-mail, or serve web pages. Instead they direct web surfers and e-mail messages to the correct computers.
What is involved in making a domain "work"?
By "work" I am assuming that you mean setup a web page at your domain name, or enable e-mail addresses at your domain name.
The short answer is that most people simply hire a hosting service to look after their needs, which means you simply need to get the DNS servers for the domain set to the DNS servers that the hosting service operates, and they do everything else.
The long answer is that you need to get a computer (#1) configured to handle your e-mail and/or serve your web pages. You also need to get a computer (#2, a DNS server) configured to answer DNS lookups and refer requests to the first computer.
Can I make my domains work myself without hiring a hosting service?
If you are comfortable adding and configuring new software, and you have a computer connected full time to the internet, then the answer is probably "yes!" Of course, there are many good reasons to use a competent professional hosting service, but for casual or experimental use, a home computer can do fine. (Also, there are various free services on the net. You may be able to combine free dns with free webspace.)
DNS servers generally require static IP addresses, so they are not usually run from ADSL and cable modem connections... but there are a number of free and non-free DNS services (see the Google Directory or our domain-dns.com service).
There are many solutions for web server software, so I'll just provide a link to the Google directory. (Note that there are subdirectories for Windows, Macintosh, and Unix software.)