Shigeo Shingo was a Japanese industrial engineer who was celebrated for improving manufacturing practices at Toyota among other companies. In the 1960s, in an effort to improve manufacturing assembly lines, he created poka-yoke. Poka-yoke is the concept of preventing/stopping mistakes through smarter design. For example if a machine required a worker to only press a button with their right hand, their left hand could still accidentally be hurt by the machine. So the machine would be redesigned to only operate if you pressed one button with your left and a second button with your right hand, ensuring that both hands would be clear of the machinery. Poka-yoke looks to prevent a mistake and teach you the correct method at the same time.
Poka-yoke is seen in our daily lives in a variety of things. Electrical plugs are designed with different sized plugs so they can only be plugged in one way, preventing you from making a mistake. Some cars require pressing the brake before you can move the car out of park to prevent the car from moving before the driver is ready. Child-proof pill bottles include an extra step to prevent children from opening the bottles. Surgeons and pilots follow procedural checklists to avoid simple mistakes and ensure safety.
Most user experiences are open-ended allowing users to filter and move between pages with few restrictions. However, when following a serial process (such as the checkout process in e-commerce), or closing an unsaved file, UX designers use poka-yoke to prevent mistakes. In e-commerce, designers will remove unnecessary navigation that could take the user away from completing the checkout. When attempting to close an unsaved document there is an interstitial / chicken message warning you so you can save the document and avoid losing your work.