There are many new TLDs these days. For example, .com is a TLD, and .org is also a TLD. These TLDs identify the domain name uniquely so pspinc.com is not the same as pspinc.org. With new internet industry rules, you can purchase your own TLD if you want (it is about $150K for you to buy one). You may have seen some new ones already like .ninja, .book, .accounting, etc. Those who purchased TLDs may intend to sell the domain names with these TLDs.
Sometimes TLDs also contains country codes. For Japanese domains, it is co.jp or ed.jp. Each country has its own rule; for Japanese TLDs, you must have an address in Japan, and for commercial TLD (co.jp), you need to be registered as a business with the government.
Only 25 years ago, the number of domains in the world was in the tens of thousands, but now there are over 326 million domains as of last year, and close to 900 TLDs available in the world! Some are considered to be spam heavy so my recommendation is to stick with .com if you can.
Even then, it is hard to find available domain names today that aren’t already taken. And you really want to be particular about your domain because it will be unique to only you. It will be how you are identified online and it can play a big role in your search engine performance. For example, we own a domain called japanese-online.com for free Japanese language lessons. Because the domain name contains the word, “Japanese,” our search engine results for keywords like “Japanese learning” are very good, so good that we appear on the first page of Google search.
So think strategically and decide on a name that is memorable, not too hard to recall. Maybe it’s your company name or a variation of it, like pspinc.com is short for our company name Pacific Software Publishing, Inc. Also be aware just because there is no website affiliated with a particular domain does not mean the domain is available. Here is the official site to find out if a domain name is available: https://www.internic.net/whois.html.