There are many time frames... ticks, minutes, hours, days, weeks... an infinite # of lengths of averages... 1,3,5,10,20,50,100,200 etc and many types of methods to calculate moving averages... weighted, exponential,simple, geometric,displaced,triangular etc.
They are all valid in that they can help show short,medium and longer term trends but they all generally have the attribute of being lagging indicators... measures of past price movements which isn't necessarily bad although people have to realize they are lagging and not "predictive" indicators.
Actual price action which moving averages are derived from has no lag which is why I prefer trading from actual prices rather than averages... but if a person develops a moving average trading method that works... more power to them.