Most people will know how to swim at least a little bit; almost everyone can do the dog paddle, for example. Different styles of swimming, however, demand a more complete knowledge of how to perform each stroke differently. This can be taught easily once certain basic elements are explained. The easiest way to learn how to swim is through use of diagrams of swim strokes. There are many ways to find these.
The easiest way to find information these days is, of course, the internet. If you open your favorite search engine - for example, Google or Bing - and type in the keywords "swimming strok" or "swimming stroke diagrams". In this case, it is best to use the quotation marks around your search string, so that you will get only relevant results. Sort through the results until you find the ones which best illustrate the strokes you are trying to learn; at that point, you can print out the instructions or save the relevant images directly to your computer. You can also search for specific strokes by name. For descriptions of some of these strokes, read on.
The most common stroke, freestyle, can be broken down simply. The body, in the water, is elongated stomach down, parallel to the water and the feet kick in a "flutter" style. Each foot moves up and down in different directions repeatedly. The arms move in much the same manner, extending far out in front of the body and pulling the body forward with each stroke. As one arm moves forward, the other is behind the body, preparing to repeat the motion. The backstroke, another form of swimming, is done the exact same way, but while laying on your back instead of your stomach on the water. The head should be slightly tilted to allow easier breathing access.
The breaststroke is possibly the most common yet complex stroke to learn. It is performed by laying on your stomach, parallel to the water. The legs move in a frog like pattern, kicking out to the side while propelling your body forward, and straightening before kicking again. At the end of each kick, the heels of the swimmer should tap each other before releasing to kick again. The arms move in much the same motion, pulling water from straight out ahead of the body towards the chest after each kick. This stroke is performed by kicking the legs first, and following with the arms. A breath is allowed after each kick, as the kick when demonstrated properly pushed the body above the water slightly.
The butterfly is the most difficult to accomplish of all the strokes. The body is parallel to the water, stomach down. The arms move at the same time throughout this stoke in a circular motion, propelling the body by reaching out in front of the body and pulling water towards the hips. The legs move after each arm motion, but kicking downwards very hard at the same time. The kick allows the front of the body to be lifted slightly, allowing the swimmer to breathe if needed.
Other places to find diagrams of swim strokes include your local library; go to the recreation and sports section of the library and you should be able to locate several books which detail how to swim. You can also ask at your local pool or YMCA. They will often have guides for new swimmers which include swimming stroke diagrams.