Every website can be found by a numeric address known as the Internet Protocol address or IP address. The IP address for this website is 75.126.41.210 which can be hard to remember. The domain name is nicfair.com which is much easier to remember. This domain name needs to be registered with an organization called a domain registrar which is then capable of informing all of the internet routers how to find nicfair.com. They know that the website exists on a server accessed through nameservers, which are addresses which point to a specific server or array of servers. The server then knows how to route incoming requests to the proper IP address and you get our content sent to your browser.
The extension for nicfair.com is the .com part. Originally when the internet was set-up, there were three extensions, .com, .net, and .org. ".com" was meant to be used for commercial (business) websites, ".net" for internet service providers, and ".org" for non-profit groups and organizations that were neither a business nor a service provider. However, now that convention has gone by the way side and you can find a variety of all types of sites using the extensions interchangeably.
There are also extensions that are country specific. You need to be living in or doing business in many countries in order to get those extensions, but not all. For instance in the USA you can get ".us" and in Canada you can get ".ca". In Great Britain they use ".uk". The one most widely known is .com. If you can, get the name you want with a .com extension.