Editor's note: After a China Eastern Airlines jet crashed in South China's Guangxi autonomous region, rescue teams have been trying their best to search for the black boxes, because they are important to explain to everyone what happened. So what are black boxes and how's the search work going?

What are black boxes?

Black boxes are flight recorders placed in an aircraft for the purpose of facilitating the investigation of aviation accidents.

An airplane actually has two black boxes. The flight data recorder captures such information as altitude, airspeed, heading and engine thrust, which can reveal whether human error or instrument problems contributed to an accident. The cockpit voice recorder preserves pilot voices and cockpit sounds.

What do they look like?

The black boxes are not black. They are painted bright orange to aid in their recovery after accidents. The exterior is attached with stripes of reflective tape.

Where are they placed?

The black boxes are usually placed in the tail of a plane where they are more likely to survive a crash.