Any commercial aeroplane or corporate jet is required to be equipped with a cockpit voice recorder and a flight data recorder. It is these two items of separate equipment which we commonly refer to as a 'Black Box.'
Besides, what is the black box made out of?
The outermost shell is a case made of hardened steel or titanium designed to survive intense impact and pressure damage. The second layer is an insulation box while the third is a thermal block to protect against severe fire and heat.
Why do they call it the black box?
The black box is a more general term for the Flight Data Recorder and the Cockpit Voice recorder of an Aircraft. Coming to your question, these 'black' boxes are actually painted with a heat-resistant bright orange colour in order to make them easier to find in the wreckage resulting from the crash.
Can you destroy the black box?
There are a handful of cases in which black boxes have not been recovered, and a couple of cases in which the flight data recorder was found but not the cockpit voice recorder, or vice versa. Rarely, a recorder is recovered but blank or too damaged to read.