After Effects nested comps, Motion equivalent?

Question

I'm trying to get an overview of how Motion works.
By way of example, in After Effects, nesting of compositions is the primary way of building up a project.
Each comp is sized (in AE) to suit its intended purpose and content, and then placed (nested) into an ever higher hierarchy of compositions until one represents the final display of the project.
What's the equivalent terminology and approach to working like this in Motion?
Or is it done completely differently?

Answer 1

That's not quite right. Groups can be imported/exported between projects. Groups can have their timing in the timeline trimmed to start and end points. Groups can be sized (2D groups, set the dimensions manually to the size you require — unless you have a very specific need for this action, don't do it - 2D groups do not interact with 3D groups other than by "layering".)  [Default groups are as large as the content contained within them - they're "dynamically" sized. If you Flatten a 3D group, you will force it to the size of the project Canvas. ] Groups are "infinitely" nestable. Groups can be locked. Groups have their own coordinate system so that everything inside a group is maintained within that "universe".  Move that group and everything inside that group goes with it perfectly aligned with everything else within that same group.
You can save your sub-projects as a regular Motion project and import them back into other projects. Motion will "unwrap" the project into the original groups and layers.
Another slick trick is to put pieces of a project into a group and drag that group into Library > Favorites for use in other projects later on. Make sure you give the Group a name you will recognize later on!
You can select Favorites in the Library pane and click the + button at the bottom of the column. You will get a new untitled folder in the "theme" section. Rename the folder and pile all of your project into the folder.  In subsequent projects, you can select all of the contents and drag them into the new project. There are some caveats to this: Rigs break. Some media might become disconnected (especially in the presence of Rigs) and Published Parameters do not copy over, so save your sub-projects before you get into rigging and publishing parameters (those should only be handled in a final project anyway.)
Best of luck!