Before defining the word "swimming", we must first define the word swim. The definition of the word swim as it relates to this article is to move through the water by means of the limbs fins or tail. Moving through the water includes floating, treading, descending, ascending, forward propulsion, backward propulsion and can even be broad enough to include snorkeling, skin diving, freediving and even scuba diving. With that in mind; swimming is therefore the act, sport, or technique of one that swims.

When one thinks of swimming, they usually associate it with someone moving at the surface of the water using their arms and legs in one of many pre-determined repetitive patterns called strokes or crawls. The difference between a stroke and a crawl is that a stroke uses a sequential pattern of arm and leg movements to accelerate the swimmer through the water in short bursts of forward motion. Crawls, on the other hand, are arm and leg movements that propel a swimmer through the water in a continuous forward motion. Because the forward motion of the crawl style is continuous, it covers more distance in a shorter period of time than the stroke style of swimming.

The names for the various strokes used in swimming usually stem from the body position in the water such as the side stroke, breast stroke or the back stroke. Others such as the butterfly or dog paddle are so named because of their resemblance to the movement the creatures for which they are named. There are others which are named after people who introduced the particular style and even after countries in which the style was first developed. While there are many variations on a theme, the variations all stem from four basic styles which are the front crawl, backcrawl, backstroke and breast stroke.

In competitive swimming the swimming styles used for competition are limited to the Breaststroke, Butterfly and Backstroke with a rigid set of rules on how each stroke is performed. The only events in competitive swimming that allows the competitor to use variations of strokes is the Freestyle and one leg of the Individual Medley.

While one might think that swimming is only done at the surface of the water, the definition of swimming also includes propelling oneself forward beneath the water as well. There are even competitive events for that which are explained in the article on freediving.