Where is the backbox keep and what is it made of and how does it record?

Answer 1

Actually, there are 2 per plane.
One records certain control settings, such as throttle settings, flap settings, AOA (Angle Of Attack), etc.
The other records cockpit voice conversations/noise. (Cockpit Voice Recorder)
As mentioned earlier, they are high visibility orange.
They are located in the rear section of the aft cargo bay.

Answer 2

Strange question, why does a civillian need to know?

I'll tell you how the last generation worked. Various telemetrics of the aircraft such as speed, heading, altitude, flaps, etc were recorded on a metal cassette the "tape" was a roll of metal that was etched by a stylus. The recorders were orange not black, most made by Fairchild. The box resembles a saftey deposit box over 2 feet long 8"X6" The DFR's also have a homing signal so that recovery teams can quickly find it and turn it over to the NTSB.