This has been discussed a few times so a search might be helpfull.
The Running Boards are relitivly flat extruded alluminum pieces with plastic end caps. They run almost the length of the side from wheel well to wheel well. They fit tight to the body.
These look much like what you see standards on many SUVs (Explorers, etc.)
The Side Steps are round Aluminum tubes that are flattened under each door with a plastic step pad. They are slightly shorter than the wheel well to wheel well length. They have a small gap between the tube and the body.
These look much like a number of aftermarket Step Tubes seen on "Sport Trucks". (I think the Honda ones are nicer than most)