Controls what the assigned actors will collide with.
Good for most actors. These will collide with all "physical" things: other default actors, navigation actors, and the non-MRE environment. It also blocks the UI cursor and receives press/grab events.
For "non-physical" actors. Only interact with the cursor (with press/grab events) and other holograms. For example, if you wanted a group of actors to behave as a separate physics simulation from the main scene.
For actors considered part of the environment. Can move/teleport onto these colliders, but cannot click or grab them. For example, the floor, an invisible wall, or an elevator platform.
Actors in this layer do not collide with anything but the UI cursor.