Domain names are available in different top-level domains (TLD) or extensions. A TLD is the part that comes after the actual name. For instance, in wpbeginner.com, the .com part is the TLD.
The .com is also the most popular domain extension. We recommend our users to stick with .com when choosing a domain name.
Other common domain extensions include .org, .net, .info, .biz, and more.
Apart from top-level domains, there are also country-code top-level domains or ccTLDs. For instance, .co.uk for the UK, .de for Germany, and so on.