The Irish Contrarian has defined moving averages very well, so I will not repeat that here. Instead, I will explain to you how to make money trading with moving averages.
Some people use one moving average, others use a combination of these.
If you use one moving average, try the 8period simple moving average. When price closes above the 8SMA, you open a long position. You then place a stop 1 tick below the low of that candle, then trail that stop up as price goes up.
Consequently, when price closes below the 8SMA, you open a short position. You then place a stop 1 tick above the high of that candle, then trail that stop down as price goes down.
Trading with one moving average can cause a lot of whipsaws, so other traders trade with 2 moving averages. Trading with 8SMA, I find the 50EMA as a good complement moving average. If you put these two moving averages over a chart, you will be able to define good entry and exit points.
Still another way of trading with MA's is using three. I sometimes add a 200EMA with the above mentioned MA's, but, if you looked at any chart with these three MA's, you will find that their entry and exit signals will be different.
Google "trading with moving averages" to find more information on this. FInd one that will suit your trading methods.
Hope this helps.
- Jim http://jsforex.blogspot.com