A texture that is rendered directly, as a visual. Decals are rendered into a viewport-aligned rectangle.
The color that, in the case of blitting, will be replaced or, in the case of overlays, be covered up on the destination surface.
A light source that is attached to a frame but appears to illuminate all objects with equal intensity, as if it were at an infinite distance from the objects. Directional light has orientation but no position, and it is commonly used to simulate distant light sources, such as the sun.