Hemming is the alteration used to shorten the leg length of jeans, most often because the inseam is too long for the wearer's height or for a particular pair of shoes. The process typically involves cutting away excess fabric, folding the new raw edge under, and stitching it down to create a clean, finished bottom edge at the desired length.
Two common approaches exist. A standard hem removes the original hem entirely and creates a new one at the shorter length, which is quick but loses the factory finished edge, including any fading pattern that had developed there on worn jeans. An original hem alteration instead removes fabric from higher up the leg and reattaches the original hem, preserving its factory stitching, wear or fading, which many people prefer for jeans that already show some fade.
Getting the length right before cutting matters, since hemming cannot easily be undone. See our guide to hemming jeans for step by step advice, and how should jeans fit for judging the right length beforehand.