Liquid crystal is a special mixture with solid crystal optical properties and liquid flow characteristics.
When the liquid crystal molecules are arranged by the external voltage  ,the incidentlight would be deflected.
The work principle of LCD/Liquid Display (Crystal) is based on the light transmission or blocking introduced by the liquid crystal molecules which are placed between two pieces of conductive glass. The arrangement of liquid crystal molecules are driven by the electric field effect between the two electrodes to control the light switching and image display . A color images could be displayed by adding color filter.