Shutter Speed is the length of time light falls onto the recording media. The main rule to remember in regards to shutter speed is that the exposures with faster shutter speeds require more light than exposures with slower shutter speeds.
For most cameras, shutter speed is displayed as whole numbers which in actuality are really fractions. For example, in numbers such as 60 in the view finder or on the LCD is really 1/60th of a second. Slower shutter speeds will display quotations marks which indicate a measure in seconds. So, say for example you had a shutter speed of 0.6, this is really 6 tenths of a second or if you had a shutter speed of 2.0., this is really a shutter speed of two seconds.
Let us look at two shutter speeds in real time. This would be a shutter speed of 1/30th of a second. And this is a shutter speed of two seconds. Lastly, shutter speed that you may see in your view finder is bulb and this refers to leaving the shutters open as long as you would like. Now, generally speaking fast shutter speeds will allow you to capture faster moving objects. Take a look at these pictures from the park. I decided to take some pictures of a water fountain particularly the water droplets themselves moving through the air. As you can see the faster the shutter speed the more still the droplets appear.
Now, there are few important barriers to keep in mind when considering shutter speed. The first is 1/60th of a second. If you are shooting people, this is usually the safe barrier. Anything slower than 1/60th of a second will increase the chance that it will be blurry. And the reason is people move, you move and your subject may move. If you are attempting handheld pictures at shutter speed slower than 1/50th of a second without a tripod or without an image stabilized lens you are probably kidding yourself and you are probably wasting your time. So, keep that in mind when you are shooting people 1/60th of a second. If you are shooting in moving athlete usually 1/500th of a second will be enough to freeze the action. It really depends on what you are trying to do. But for beginners keep this in mind, 1/500th of a second for moving athletes.