This program uses the example of a small company's monthly sales figures to demonstrate the ideas behind time series and moving averages.
By clicking on the graph you can build up a data set of a year's figures. This is a time series. Try it.

If you tick the "Moving Averages" box at the top of the page you will be able to see the moving averages for the data. At the bottom you can choose to look at 2 month-, 3-month- moving averages, up to 6-months. If you watch closely what's going on, you'll see how moving averages are calculated and plotted on the graph, and how they are related to the time series.
Play around!