I need some clarification... could someone compare and contrast groups and layers in Motion. Maybe tell me what the differences are in the terms...
What is the relationship between the two?
Will I use both in a composite, give an example maybe of how you would use the two together in a composite.
Layers are elements (including lights and camera) of your comp. Groups are folders that you can group layers (lights and camera) under the same group. What I usually do is to use groups as a way to put elements (layers) together and then I can move all this elements in the comp by moving only the group. Example: If you have a animated text you created made by a few different layers of text and lets say a animated background you can then put all these layers under one group in will to move them together in your comp in will to be quicker. On a 3d comp this could be quite important as you might need to adjust the Z axis of a few elements and you can do this with all these elements under one group.
You can also apply some effects to the group and it will work on all the layers. (it might not work with some effects and some kinds of elements). When creating a complex comp it is key to use this well or you will be swamped in an ocean of layers and will be hard to find stuff.
Hope this helps. I am sure that once you understand how to use it, your comps will be more organized and more efficient when changing.