Yard signs are usually made of corrugated plastic with wire stands. These are temporary signs for advertising in yards and on roadways.
Real estate signs are generally made of aluminum in aluminum stands. They are very useful for longer lasting signage which needs to be moved frequently. A-frames and sidewalk stands are another option for moveable signs.
Site signs are larger signs for construction sites and commercial real estate. They are generally made of wood or aluminum faced materials and mounted on wood posts.