In swimming, there are four strokes. These strokes are butterfly, backstroke, breastroke, and freestlye. The first of the four, butterfly, is swam by kicking both legs up and down while your arms simaltaneously move together, pulling water with an out of water recovery. The second stroke, my personal favorite, is backstroke. Backstroke is swam by kicking your legs (not together) up and down while your arms individually pull and recover out of water. The reason it is called backstroke is because it is swam on your back. The third is called breastroke, and it is swam by kicking your legs similarly to how a frog moves it's legs, and your arms move in a circular motion in front of you, pulling water, but this time there isn't an above water recovery. The final stroke, freestyle, might also be called the front crawl, and is the most commonly known and swam stroke. Freestyle is swam just like backstroke, but on your front.
This is an example of butterfly