Cuff alignment (sometimes called cant adjustment) lets you tilt the upper cuff of the boot slightly left or right relative to the lower shell. This accommodates bowlegged or knock-kneed stances so your knees track properly over your toes and you can engage your ski edges evenly on both sides.
You'll benefit from this feature if you struggle to hold an edge consistently on one side, or if you've noticed your knees don't stack neatly over your toes in a natural stance. Most performance-oriented boots include cuff alignment, but many entry-level models skip it to keep things simple.
The catch: don't just crank the adjustment yourself and hope for the best. A bootfitter should assess whether you need it and dial in the right angle. Also, cuff alignment alone won't fix every stance issue—custom footbeds are often the missing piece for proper alignment from the ground up.