Swimming describes any method by which humans (or other living creatures) move themselves through water, apart from walking on the bottom.
Swimming is a good way to relax, with many swimming styles suitable for recreational swimming. Most recreational swimmers prefer a style that keeps their head out of the water and uses an underwater arm recovery. Swimming is also a good form of exercise. Because the density of the human body is approximately similar to that of water, the body is supported by the water and therefore less stress is placed on joints and bones. Furthermore, the resistance against movement depends heavily on the speed of the movement, allowing the fine tuning of the exercise according to one's ability. For this reason swimming is frequently used as an exercise in rehabilitation after injuries or for the disabled.
Questions that should have this tag deal with, e.g. swim techniques (stroke, breathing), injuries, dry-land exercises, open water swimming, swimming in combination/relation with other physical activities or work-out routines for swimming.
See for example these questions to learn more about Swimming at this site: