If you're having trouble finding a domain name (whether because of crowding or cyber-squatters), check for a help facility on each registrar's site. Domain registrars typically house search engines that return a listing of available names similar to the one you want. When you search for a domain name at Namecheap, for example, you get both the status of that name and a list of suffixes available for that name. Maybe [Sitename].com isn't available, but [Sitename].biz or .org is.
Registries and registrars usually charge an annual fee for the service of delegating a domain name to a user and providing a default set of name servers. Often, this transaction is termed a sale or lease of the domain name, and the registrant may sometimes be called an "owner", but no such legal relationship is actually associated with the transaction, only the exclusive right to use the domain name. More correctly, authorized users are known as "registrants" or as "domain holders".
Domain names were created to make IP addresses easy to remember. Every computer has an IP address assigned to it – much like a street address. But instead of having to memorize each IP address number, we assign domain names to these numbers so we can easily remember them. The domain name system, or DNS, takes domain names and translates them into their IP addresses so that computers can communicate with one another. When you enter a domain name into your web browser, the browser simply uses that domain to locate its corresponding IP address and then shows you the website associated with it. If you own a business, GoDaddy can help you find a domain name that best suits the business so you can easily promote your website.
Some domain names are only available at auction. For now, we’ve chosen to feature buy it now domain names because they are often available immediately. We are working to improve our search engine to make it easier for advanced users to choose whether they want to include domains at auction (or domains with hyphens and numbers) in the search results.
SnapNames is a web domain name marketplace - meaning that they only deal specifically with domains that are currently owned by somebody else. They offer daily and premium auctions, private brokerage of domains, and buy-it-now listings for buying and selling domain names, including over 30 million domain names that aren't all, as you'll find on some services, exorbitant. They have over three million customers, including a significant number of small businesses, which is worth it.
The top ten was rounded out by #8 Ecig.co.uk ($6,613 at DomainLore.co.uk) and two more Sedo sales - #9 Wallace .co at $5,999 and #10 Poianabrasov.ro at $5,632. Sedo went on to sweep 16 of 20 chart entries overall. UnicDomains filled three spots with sales they made on the Above.com Marketplace with their marquee sale of #4 AR.ca ($25,000) joined by #12 (tie) Playground.ca ($5,000) and #20 BlackMarket.ca at $3,500. 
A few companies have offered low-cost, below-cost or even free domain registration with a variety of models adopted to recoup the costs to the provider. These usually require that domains be hosted on their website within a framework or portal that includes advertising wrapped around the domain holder's content, revenue from which allows the provider to recoup the costs. Domain registrations were free of charge when the DNS was new. A domain holder may provide infinite number of subdomains in their domain. For example, the owner of example.org could provide subdomains such as foo.example.org and foo.bar.example.org to interested parties.
Sedo is where I bought my domain - over Escrow - and is a global marketplace to buy, sell, and park domain names. They've over 18 million domain names for sale, but the big part is that they're a huge, well-respected company. This may not be important if you're spending $150 on a domain, but in a $15,000+ purchase - which happens in many cases - you will be potentially buying from a foreign entity, that you don't know, and many of them will suggest an escrow payment. This means you put the money in an account owned by a third party that will hold it and only pass it on once the domain has been transferred over into their name (which in this case is what Sedo does). This can be quite disconcerting - but Sedo is well-known and has done many, many deals - and the process is about as full of hand-holding as handing tens or hundreds of thousands of dollars for a domain name can be.
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Second-level (or lower-level, depending on the established parent hierarchy) domain names are often created based on the name of a company (e.g., bbc.co.uk), product or service (e.g. hotmail.com). Below these levels, the next domain name component has been used to designate a particular host server. Therefore, ftp.example.com might be an FTP server, www.example.com would be a World Wide Web server, and mail.example.com could be an email server, each intended to perform only the implied function. Modern technology allows multiple physical servers with either different (cf. load balancing) or even identical addresses (cf. anycast) to serve a single hostname or domain name, or multiple domain names to be served by a single computer. The latter is very popular in Web hosting service centers, where service providers host the websites of many organizations on just a few servers.

A fully qualified domain name (FQDN) is a domain name that is completely specified with all labels in the hierarchy of the DNS, having no parts omitted. Labels in the Domain Name System are case-insensitive, and may therefore be written in any desired capitalization method, but most commonly domain names are written in lowercase in technical contexts.[2]