Interestingly enough, .com describes that a web site has some kind of "commercial" intent. This is what we call a "top level domain" address, and it used to be a way for a web site to convey its publishing intent.
When the World Wide Web was launched in 1989, these top level domains were used to help categorize the few hundred web sites at the time. Historically, .com web site addresses were for those publishers out to make some kind of profit through their Internet services.
No, having a .com domain name does not mean your web site is a licensed business. In fact, the Internet registration authorities have expanded their criteria to allow most anyone to have a .com address, whether you have a commercial intent or not.
Today, having a .com domain name has no special significance, other than people perceive it to mean you are a serious Internet web site. Other than perception, .com has no technical difference from a .info or a .biz top level domain name.
Related: there are other top-level domain addresses available to the general public, like .org, which is used to denote "non-profit organization", and .net, which is generally used to denote "network and computer" topics.
Techno trivia: three-letter top-level domains, like .com, .net, and .gov, are nearly always American web sites. Two-letter domains, like .jp and .ca and .co.uk and .nz, are for other countries other than the USA. These country TLD's indicate sites that are published from that part of the world, or that the web site owner is a citizen of that country.
Top level domains with more than three letters: Several new domain names, like .info and .shop, have recently become available since 2005. This is in response to the huge growth of the Web, and that domain name addresses were running out.
Read the full explanation of web URL addresses here.