Looking to make vegetation leaves or possibly have graffiti line the walls of your subway scene? Then the alpha-based material type is definitely the one you are looking for.

Sometimes you are just after a color or texture map without having it reflect in a scene. Common usage would be in 2D games using flat sprite geometry. In this case diffuse materials are the simple material you are looking for.

Sometimes coined as "physically-based materials" this type of material takes in several texture types to reflect as surfaces do in the real world. This type of material is the most commonly used within games and cinematics.

Picture your player in a scene walking by a waterfall or possibly being directed by arrows on a race track. In these cases you would use the scrolling material type to create this effect in your scenes.

Much like the alpha-based material the vegetation material allows for foliage to be shown in the world. The main difference being with the vegetation material is the ability to apply wind effects to the vegetation to make it sway.