What Is A Faraday Cage?
A Faraday Cage (Shield) can be described as an enclosure created
by conducting materials
that blocks external electric fields (both static and non-static).
These shields – cages can be used to protect different kinds
of electronic equipment from electrostatic discharges.
They can't block magnetic fields like Earth's magnetic field,
but they can protect the interior from electromagnetic radiation
coming from the outside.
How Does It Work?
An external electrical field leads to rearrangement of the charges,
and this cancels the filed inside. Electric fields (applied externally)
create forces on electrons in the conductor, creating a current,
which will further result in charge rearrangement.
The current will cease when the charges rearrange and the applied field inside is canceled.