Side kick (Yop/Yeop Chagi)
A straight, sideways kick that drives the heel (or foot blade) into the target. From fighting stance, turn your hips sideways, chamber by pulling your knee to your chest, then thrust your leg straight out so the heel hits the ribs/abdomen (or head for high kicks). Re-chamber quickly and set the foot down with your hands guarding. Think: knee to chest → heel to target → snap back.