WPT details: https://wpt.fyi/results/css/css-scroll-snap/scroll-snap-stop-always.html
Normally an inertial scroll operation (such as a swipe gesture) may skip several possible snap positions in favor of a snap position that is closer to its natural end point (which depends on platform and gesture characteristics such as velocity). scroll-snap-stop enables authors to designate a snap position such that it traps the inertial scrolling operations preventing the scroll from skipping it.
Some forms of paginated scrolling experiences require user scroll gesture to move at most a single page. A common example of this are full-sized paginated image carousels where they move one image at the time. This feature enables css scroll snap to support such usecases.
Docs: https://snap.glitch.me/carousel-with-snap-stop.html
Explainers: https://drafts.csswg.org/css-scroll-snap/#scroll-snap-stop