Explain Class A amp to non audiophile friends

How do I explain a Class A amplifier and a Class A/B amplifier to my non audiophile friends? I tried by saying a Class-A amplifier power devices are conducting a continuous current meaning they are always on. They did not understand and maybe neither do I.

Can someone please explain how a Class A amplifier works vs a Class A/B amp in non technical terms so I can explain it to my friends.