There are organizations that are called registries that manage each TLD option. When you register domain names, you would first visit a domain registrar who would in turn check with the registry that manages that TLD to see if the domain is available. If the domain for the TLD you want discovers that it is in fact available, the registry adds it to their registry and gives you access to it. If the domain has already been registered by another user for that TLD, you will be shown during the domain registration process that the domain isn't available.
GoDaddy used to be a place I'd recommend only as a joke, but has significantly improved their service. They'll recommend you domains based on certain keywords, which is useful if you've not got the one you want available (they'll actually remove these from the search to try and not break your heart), and they've also significantly improved their hosting offering. They still continue to offer weird things like "email services" that other hosting companies provide too. Our GoDaddy Review.
If you do not have a web host, you can always allow the registrar to park your domain name at a temporary website specially set up for you. This way you can quickly secure your domain name before it's too late and still take your time to set up the other aspects of your site. As far as I can tell, most registrars (or probably all) automatically park your domain by default whether you ask them to or not, so if this is your situation, you probably don't have to do anything special to get it done. Some of those registrars also provide you with a free email address at your own domain name while it is parked at their site, like firstname.lastname@example.org (where "example.com" is your domain).
While numbers like the ones seen above are impressive, most domains sell for significantly less extravagant prices and are generally in the two or three-digit range. Not long ago, those who were able to secure general terms (like icecream.com or pizza.com) not protected by trademark rights often found themselves sitting on virtual gold mines. The glory days of this boom have long since passed, and those looking for a profit in today’s market need a keen sense for coming trends.
When you type google.com into your browser, the domain is split into parts by the “dot”, from right to left. The first part is “com”, so your computer checks the root zone file to see which registry manages the .com TLD. It then checks with this registry to see where the next part, “google”, points to. The registry returns the IP address 188.8.131.52, and your computer can then ask Google to send their homepage over.
A great domain name is a concise, easy to type, and memorable URL that reflects your brand or your website’s subject matter. Avoid using hyphens, strings of numbers, or unnecessary words to make it easy for your visitors to remember and find your website. Remember: A great domain name is one that your visitors can type correctly on their first try.