In plain language
Features that use swipes or multi-finger gestures need a simple tap/click alternative.
Who it affects
People with limited hand mobility and users of head-pointers, sticks, or eye-gaze systems.
How to check
Find every gesture (swipe, pinch, two-finger): confirm buttons or another single-tap way to do the same thing. Worked example — A photo-sharing app's upload screen: try tapping a refresh button instead of pulling down: if pull-to-refresh is the only mechanism, it fails.
Common misconception
A swipeable carousel with dots underneath feels complete, but the dots are often just indicators, not clickable controls. The rule needs an actual tap/click alternative to the swipe gesture. Real example: on an online clothing store's product listing page, a feature requires drawing a path/swipe gesture and offers no simple tap/click alternative.