Blender 2.8: Layers, Collections & Overrides
Layers and groups have been replaced by collections. These are used for organizing objects in a scene, instancing groups of objects, and linking groups of objects across .blend files.
Objects in a scene can be organized into named and nested collections, no longer is there a limit of 20 unnamed layers.
Hiding collections is done in the outliner or by using Ctrl+H in the 3D viewport. This is a quick way to view and work on just a subset of objects in the scene. Hiding such collections merely makes them invisible in the 3D viewport, but they are still part of the scene.
Collections can also be enabled and disabled for the viewport and rendering. This can be used to indicate which collections are intended to be rendered or visible in the viewport for the task at hand. This state can also be animated or driven.
Collections do not have to be part of a scene, and can also exist on their own. This is useful for example to limit physics collision to a subset of objects in the scene, or
These loose collections can be found in the outliner, by going to the Blender File view and filtering to show all Collections in the file.
Render layers have been renamed to view layers, to indicate their expanded scope. Besides splitting up a render into multiple layers for compositing, they can now also be used as multiple views and variations of a scene.
Blender 2.8 introduces a general override system, to replace the limited proxy system. Overrides can be used to animate linked characters, or to make variations and local modifications of linked materials or lights. When the original data changes, overrides are preserved and applied on top of the modified data.