Explaining a concept out loud to a inanimate surrogate to find problems, clarify ideas.
”Rubber Ducking” is the action of explaining a concept out loud to an inanimate audience surrogate, such as a rubber duck, with the goal of finding bugs in code, or clarifying your ideas. The object is pre-supposed to know nothing, so you have to explain what the code is doing, or how your concept works, from scratch in a way that it could be learned.
It’s sort of like active listening for your own thought process. Or an excuse to employ the Feynman Technique.