how the operation circuit and function for LDR? Answered

Depend on what your going to do with it.

A Light Dependent Resistor is a device that changes it's resistance as light falls on the face.

The resistance goes down when lit and up when dark.

I general they are placed in a potential divider circuit so as the LDR changes resistance the voltage at the LDR/resistor junction changes.

http://www.rev-ed.co.uk/docs/picaxe_manual3.pdf page 29