The first is the arch bridge. How an arch bridge works is that the arch bridge is shaped with a curved arch. That transfer’s weight by it loads in to a horizontal thrust that is restrained by the abutments on either side. There is also a key stone on the arch that holds everything together.
The second is the truss bridge. The truss bridge is formed of connected elements. The connected elements sometimes are stressed by tension, compression, and the response to the dynamic loads. So the way it works it uses the tension and compression from making the pathway from falling.
The final bridge is the suspension