Kettlebells work by placing a compact weight below a handle so the load can swing, rotate, rest against the body, or be carried in ways that feel different from dumbbells and barbells. The offset shape changes timing, grip, balance, and how force moves through the hips and trunk.
That design makes kettlebells useful for swings, cleans, snatches, carries, goblet squats, presses, and conditioning circuits. The same design also means technique matters: the bell should match the movement, the user's skill, and the available space.