tray style floor liners

MAXLINER All-Weather Floor Mats front and back. $ 69 Shipped OBO. Interested Please PM Thanks Shad

This may sound like a stupid question, but I'm a little confused as to what "Tray Style Floor Liners" really are. There is almost no description of them on the build and price tool-it just says they are optional equipment. Are they essentially rubber floor mats? With a liner design so any...