Combos are a staple of many fighting games, and in Battle Royale, they are just as important. In the Super Smash Bros. series, especially Super Smash Bros. Melee, combos work a bit differently than they do in Battle Royale.
Combos: How They Work on Ground
Ground Combos work pretty simply. Each move has a certain amount of hitstun that will slightly increase with more % damage taken. For every 15%, the amount of frames increased for the hitstun will be one. Damage does pile on, so an attack that deals 20% will add the one frame. Jabs are not affected by this; the default hitstun is the permanent hitstun.