Anyone can buy a domain name. To do so, you visit a domain name registrar, such as GoDaddy or Namecheap, key in the domain you want to buy, and pay a fee. You can't buy just any domain, of course—only one that isn't already registered by another person or business and that bears a valid domain suffix. In general, you'll want to buy something that is catchy and short so that it's both easy for people to remember, and easy for them to type in—like "PCMag," for example. That good search engine optimization (SEO) and it's also common sense. You might also want to do some research on key terms for your business. If you can get a good one into your site's name, that's all the better, from an SEO perspective.
Perspective buyers are able to directly contact domain holders in cases where the desired domain is no longer available. Most registries openly publish the names and contact data of domain holders. Once this information is gained, buyers can get in touch with domain holders and make an offer for the name. Sales are also known to occur in instances where the original domain owner had no prior commercial ambitions
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 email@example.com (where "example.com" is your domain).
Premium domains (also known as aftermarket or pre-registered domains) are short domains, often just one word or even just 3-5 letters. Most of them have a .com extension but many premium domains end with .org, .net, and .biz. These domains include common words and are generally the most memorable. Because companies value short domains that match their company name or products, these domains are typically the most desirable. Additionally, certain domains sold by different registries are considered premium and therefore have a higher price point. In some cases, the renewal costs of these higher-priced domains are also quite expensive. Some high-priced premium domains, though, renew at a regular (lower cost) rate, giving you a better value in the long term. Make sure to research the overall cost of the domain plus renewal to find the right domain for your budget. You can browse Namecheap's premium domains in our Marketplace.