what is that green light above speaker?
That's not a light at all, just a very poor reflection for the void in the white (that's there in the black, just not very notable - people thought it was purple on the older iPhones) that allows the ambient light sensor and proximity sensor to see the light of day. The black and white color is solid, and needs a cutaway for inner workings to see through.
What is the switch at the top left above the +/- buttons?
Someone new to the iPhone looking to switch! Woohoo!