Back in the earliest days of the world wide web, the .COM domain name was intended for commercial organisations. Nowadays, the .COM domain has been adopted far and wide by everything from ecommerce sites to personal blogs, and is the most recognisable extension on the internet. Because there are no restrictions on the use of the .COM domain, it is used for a myriad of non-commercial websites, as well as those of commercial enterprises.
Many countries have introduced an extension of the popular .COM extension that includes their country code, for example .COM.AU for Australia or .COM.GR for Greece. These more localised domain extensions serve the same function as the original .COM domains, however they give visitors to a website a clue as to the geographical whereabouts of the pages that they are browsing.
Whatever your core purpose for your online presence, whether you're starting a business or want to share your personal thoughts with the creation of your own blogging site, a .COM domain name is a very good place to start.