Structures are layers you can add in your composition which will drive the animations, like the rig of a real puppet. The process is very simple: create or import your design in After Effects, add Structures and move them to the right spots (the pivots of each limb). Then you can rig those Structures, instead of the design itself like in previous versions of Duik, and finally parent the design layers to the corresponding Structure layers.
This way, the rig you create is independant from the design. This means it’s easier to adjust the design even after the rig has been made, or even to re-use the same rig with other designs. Also, this rigging process is easier to fix or change if ever you need to adjust it even when you’re already in the process of animation.
This is the Structures panel as shown in the Normal mode.