By default, VRED provides two environment switches. One is in the Material Editor and the other in the Scenegraph. Both have an icon with an orange star , which indicates a switch. These switches are connected and have the same number of children.
For information on using environment switches, see Working with Environments and Environment Switches.
What makes them different is:
Use switches, whether they are environment or something else to change things quickly. Use an environment switch to instantly set your model in a new location or to see how it will look in different lighting conditions. One minute, it's a dark garage. The next, it's the seaside in the middle of the day or Times Square at dusk. If you have clients wondering what a car would look like painted some other color, switch to the metallic blue fire or OCS Red Candy. Different interior colors or fabrics? Switch them quickly and easily, on-the-fly.