.COM is short for Commercial or company. Meaning that normally a website that uses this at the end of their URL is a company, commercial business, or for profit. This was the standard a couple of decades ago. But as of today it has become a catch all instead. It is the most common domain used. An example of the use of a .com domain extension is in the image below for Instant Accept.
You will also notice that there are many of domains such as