Applets are just small programs that deliver information to the user. Applets may be added to the panel by right clicking on the panel and choosing to add a selected applet. The applets themselves may be configured by right clicking on the applet in order to make necessary changes, like adjusting the time. Here is an example of the Invest applet to track your stocks. Right click the panel select Invest and then right click the applet to add your stocks.
The applet can track any number of stock you would like to enter. If you enter your stock ticker, the price you paid, and the number you purchased, it will track those stocks from the Yahoo website and give the information on how they are doing.
If you double click the applet you can select charts that will go with your stocks.
Applets are a great way to add features to the Desktop that enhance the working environment.