the google OPerating system.
it's installed on some smartphones - mostly the ones that now rival iphones, like htc, nexus, etc
I have an htc phone, and, imo, it's better than an iphone. looks pretty similar, acts pretty similar, but just has the edge on a few things (more htings if you are a proper geek, i expect)
android do lag behind on apps, though. but then I have my itouch, when I canwrench it away form dd1