Poka-yoke is a technique used to prevent errors or defects from occurring during a process. It works by either shutting down the process, preventing it from continuing, or sending a warning when a defect or error is predicted to occur. Examples of poka-yoke include mechanisms that prevent inserting a CD/DVD the wrong way or designs that only allow components to be assembled correctly. The goal is to design processes that are foolproof and make it difficult to make mistakes.