They replace the original ones. The old one's come right out. If they have been exposed to heat for a long time, the glue in some mats has seeped out and the mats have to be pulled out, and the glue goo needs to be cleaned out with paint thinner from the floor pan. Whatever they used to make the mats has deteriorated. Good to take them out and clean them up. However once the original mats get worn out, they are an eyesore. These replacement mats fill the void and are much easier to clean. Vacuum! And they can be customized as well to the cars color combination. PM me for more info or examples.
Happy New year!