In rendering, the environment that surrounds the objects in a scene. For example, the simulation of fine particles (fog, smoke, or dust) in the air.
When you photograph an object in the real world, it is usually within an atmosphere (for example, air) and can be surrounded by other background objects. In Maya, you may want to model only the foreground objects in a scene, represent background objects using a two-dimensional background, and then simulate the effect of an atmosphere surrounding the objects in your scene.
See also environment fog.