I'm not entirely sure what it is, but I've heard it is a serious competitor to the iPhone OS. I also heard that it is open source.

What I'm really looking to understand is whether it is a replacement OS for any phone, like Linux is to any computer. Can it work with any hardware (albeit with tweaks)? Is it something that one can install if they are unhappy with the way their phone's system functions, or am i on a completely wrong track here?

Can you tell me this info as well as similarities to the iPhone?

Thanks
Sameh