Coroplast are rigid, corrugated plastic sheets, on which signage can be printed. It is durable, washable, and weather-resistant. This material is ideal for low-cost signage, for indor or outdoor use, such as: real-estate signs, parking, construction sites, etc.
Coroplast comes in 4 and 10mm thickness, and each sheet is 48x96in.

Card Stock is a cardboard paper product, for indoor use.
This material is about 1/8in thick, and sheets are 40x60in.