I give myself a try.
Optical isomerism is quasi the ability of enantiomers to turn the light in a certrain direction. Enantiomers themselves are chemical substances which have the same atoms and functional groups, but different structures to each other, you know?
First you have a light source. This light source is producing light vibrations in all directions. Also you have a polarising filter and an analyzing filter and a plane between them. What happens now? the light vibrations are emitting to the polarising filter first. If the light vibrations touch the polarising filter, the filter allows just to pass one light vibration in one direction through. That is to say the other vibrations are 'out' of the filter. After that the light vibration is in the plane inside. The plane itself is filled with the chemical substance, one of the enantiomers. According to what kind of enantiomer exists in plane, the light is either turn in left or right direction. This turning direction can be observed by the analyzing filter. As the turning direction has something with the structures of enantiomers to do, this property can be used to get those structures out.