What is a 'Simple Moving Average  SMA'
A simple moving average (SMA) is a simple, or arithmetic, moving average that is calculated by adding the closing price of the security for a number of time periods and then dividing this total by the number of time periods. Shortterm averages respond quickly to changes in the price of the underlying, while longterm averages are slow to react.
BREAKING DOWN 'Simple Moving Average  SMA'
In other words, this is the average stock price over a certain period of time. Keep in mind that equal weighting is given to each daily price. As shown in the chart above, many traders watch for shortterm averages to cross above longerterm averages to signal the beginning of an uptrend. As shown by the blue arrows, shortterm averages (e.g. 15period SMA) act as levels of support when the price experiences a pullback. Support levels become stronger and more significant as the number of time periods used in the calculations increases.
Generally, when you hear the term "moving average", it is in reference to a simple moving average. This can be important, especially when comparing to an exponential moving average (EMA).
To learn more about moving averages, check out What's the difference between moving average and weighted moving average?

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What is the difference between a simple moving average and an exponential moving ...
The only difference between these two types of moving average is the sensitivity each one shows to changes in the data used ... Read Answer >> 
Are exponential moving averages more effective than simple or weighted moving averages?
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