LCD vs LED

Can someone please enlighten me on the major electrical difference between an LCD and an LED display. I know the major physical characteristics of the 2 (lightning, efficiency, etc).

I am looking for the major differences in electrical characteristics, like do LCD's still need current limitation, stuff like that.

Also, could you tell me how I can test some of the second hand LCD displays lying around?

LED's are current operated and require a significant amount of power, since they radiate light. LCDs are voltage operated and take very little power since they only reflect or transmit light, not radiate.

LCDs drive requirements are entirely different from LEDs. They require an AC square-wave signal for proper operation. This is normally provide by dedicated ICs that are specifically designed for that purpose. So if you want to test you LCDs, I would recommend buying such a circuit like**broken link removed**available at Digikey

Thank you for your input.