The toe of the crawl leg stretches the thigh to drive the calf to whip up and down, the sole of the foot gently lifts the water, and the instep quickly draws down. The main function of the legs is to keep the body in a balanced state, and the power of crawling forward plays an auxiliary role in the hands and legs. This is more difficult.
Butterfly legs are straight and parallel, feet close together, chest pressed down, driving the waist, making the heel out of the water, and feet bent down to fetch water. This is commonly known as dolphin kick, which is the most needed exercise and the most difficult to master.
Other moves are not limited to kicking, but the effect is not as good as the above three moves. These three strokes are the crystallization of the wisdom of our ancestors, and they are the most scientific and efficient swimming styles.
I suggest you practice breaststroke first, and then try other strokes from shallow to deep. I wish you a happy life.