What is the difference between bb and airsoft?

A bb gun pretty much works the same way as a spring airsoft gun. But the differences come in the activities of how they are used. A bb gun is used for target practice, but ever since bb guns have been created, people have been using them for fighting, like in a paintball or airsoft fight. Of course this lead to alot of injuries, (Just like in A Christmas Story). Airsoft is a whole lot different. I play it and I know alot about it. First of all airsoft is more intended for battles, like in paintball. Second of all, they shoot plastic bb's instead of metal ones, therefore having less chance of injury. Also most airsoft guns are replicated off real guns like AK-47's, M4's, Desert Eagles, MP5's, and much much more. And if played responsibly it can be a very exciting and fun activity. I started out having just backyard airsoft fights with local neighborhood friends. And now im playing professionaly at battle re-enactments, and batles. Those are the some of the differences between airsoft and bb guns.