What is the difference between a shower curtain and a shower curtain liner?

A shower curtain is for decor and hung on the outside of the bathtub/shower. Whereas a shower curtain liner is hung on the inside of the tub/shower to protect the shower curtain. In simpler terms...SHOWER CURTAIN: gets to hang and look pretty and be dry. SHOWER CURTAIN LINER: protects shower curtain from getting wet because it's the one getting wet!