Faraday Cage

A Faraday Cage is a shell made up of electrically conductive material that is closed to all sides. This shell shields the inside of the cage against electric fields and against lightning strikes. The shell doesn't have to be an entire material; a mesh made up of a conductor suffices. The body of a car is Faraday Cage.
The cage received its name from the English physicist Michael Faraday.

Here you can see a graphical depiction of how a Faraday Cage works:

If an electric field emerges between the positive and the negative pole, the negatively charged electrons move towards the side of the cage that is closer to the positive pole. The result is a charge shifting inside of the cage.
This charge shifting creates a new electric field which points exactly in the opposite direction of the outer electric field (resembled by the green field lines).
Because of this the effects of the two fields erase each other; the inside of the cage is shielded.