Moving averages are mostly only used by amateurs these days.  As has been mentioned they take the average closing price of an asset over a set period of sessions and that's the value.

The problem with this is that close prices for various sessions aren't always useful.   VWAP or Volume weighted average price is a much more useful tool because value in a market is dictated by volume.   Rejection of heaviest volume is a more powerful signal than rejection of the average closing price of whatever session you're looking at.