These are non-skid, washable kitchen rugs or mats.
They are often sold as a set of two in varying sizes, such as 20"x32" and 20"x48".
The material is typically a soft and comfortable fabric like crystal velvet or twill with a non-slip backing, often made of PVC mesh or rubber.
They are designed to provide comfort and help relieve pressure when standing for extended periods in the kitchen.