You can think of expanding and contracting as the keyboard equivalent of window snapping. But it is actually a bit more than that.
There is a new feature in town. The expand and contract window shortcuts are there to quickly resize a window until it reaches another edge. It will snap to window edges, regions and monitor edges by default
Sometimes it is useful if a window would span multiple regions, because you are focusing on something for a bit. These keyboard shortcuts allow you to do that, in a faster way than changing your regions and then resizing your windows.
There are 8 keyboard shortcuts to learn:
Expand the window leftwards.
Contract the window leftwards.
Expand the window upwards.
Contract the window upwards.
Expand the window rightwards.
Contract the window rightwards.
Expand the window downwards.
Contract the window downwards.
There is a thing to note here. The keyboard shortcuts starting with
Contracting a window means that it will shrink on the opposite side. This means that the "opposite" of Expand left is Contract right.
Customizing the behavior
This feature is implemented as 8 separate recipes. This means that you can customize how it works — e.g. by changing it to snap just to region edges and monitor edges — once you've read the next chapter of the tutorial.