Every domain name contains at least two components separated by periods or "dots." The name, and the characters after the established name or “extension.” The most popular extension is the .com, used for commercial entities. Other examples include .net, originally used for networking organizations, .org, designed for non-profits, .tv, .name, .info, and the list goes on. Anyone can register a domain name/extension.
You can also use a two-letter country code domain, such as .uk and .ca, that correspond to a country or other geographic location. The policies for registering such domain names vary; some are reserved for use by citizens of that country.
To the left of the top-level domain (the YOURCOMPANY part of YOURCOMPANY.com) is what is called the "second-level domain." These allow you to have sub sites within your master site. For example if you had a marketing campaign you could set up marketing.yourcompany.com to monitor the hits and times that the site was accessed to help determine the success of that concept.
There are many places to check the availability of your desired name, we use Register.com. If the name you want is available, get it, because somebody else, anywhere in the world could be attempting to register that same name, and in the net world, it is first-come, first-serve. If the name you want is taken (and many are), you can choose an alternative domain name, try to purchase the name from the original owner, check out if it is available for auction, try to wait out the existing owner to see if they activate a site, or let the name drop at renewal, or register the name in a different domain. If you feel that you have a right to that domain name by way of an existing trademark, you could follow the domain dispute policy to try to regain it.
ICANN is a governing body and is a non-profit corporation responsible for managing Internet domain names. More information about ICANN, as well as a list of approved registrars, can be found at ICAAN
The going rate for a domain name registration was fixed at $35 per year, but the average is $15, and some are free. Many companies offer discounted or free registration services in connection with other offerings, such as Web hosting. Registrars offer initial and renewal registrations in one-year increments, with a total registration period limit of ten years. The Domain Name Buyers Guide rates all ICANN-approved registrars available. Each company has different policies, so read the terms carefully when you register your domain name!