You can 3D Render just about anything. Rendering is economical and convenient. 3D renders allow you to view your design long before construction or manufacturing, so it facilitates refinement and better overall design.
Through animation, you can showcase complex simulations! Today's 3D modeling software have physic engines to simlate forces on materials. These simulations can show a structure under stress or a boat bouncing through waves. The flow of people through buildings can be simulated to find out the most efficient arrangement of rooms or exits, and products accurately shown in use in the desired environment.