This entry will cover the group of Compositor features that fall under the Layout category. These features help to organize your node setup and help you iterate through your design.
The Layout features can be found under the Layout field in the Add menu in the Compositor view.
The first one is the Frame. The value of the frame is that you can place nodes (or other frames) in the frame, and when you move the frame, you can move the entire group. Nodes can be added to a frame by dragging them into the frame. This is intuitive. However to remove a node from a frame you'll need to use the [ALT+P] shortcut.
By default the name of the frame is Group#. However, in the properties window [P] with the frame selected, you can change the Label field to show a different name.
Next is the Reroute node. This is basically a free floating node in space. These nodes are primarily used for redirecting the flow of the wire, or to allow branches somewhere off the originating node. These are great for organizing wires.
Finally the Switch node does just as its name implies. It allows you to switch between two inputs so you can see the difference between them very easily. This is very similar to muting [M] a node to see the difference.