To be aware means to know about. I am aware of the dangers of smoking, yet I continue the habit. You can be environmentally aware or socially aware.
Aware is a close relative of beware, "look out for." Beware the ides of March, Julius Caesar is famously warned. Too bad he's not aware of why. Beware and aware share the root ware, from an Old English word meaning "careful, wary). Be aware of your purse at all times, and beware of the snatch-and-grab thief.