There are really two things to learn about the tablet pen. The first is what you can and cannot do with it and the second is how you actually use it. There are basically five things you can do with the pen and different situations in which you can do them.
The pen can be used instead of a mouse at any time in any application in which you could use a regular mouse. The pen can provide both left and right mouse button actions.
The pen can be used to input text at any time in any application in which you could use a regular keyboard. The pen accomplishes this using Tablet PC Input Panel.
Some applications accept pen inputs and convert them into images. The images can be inserted into documents or attached to e-mail messages.
Some applications can contain the image of the ink you created and the text recognized from the handwriting. For example, Microsoft Word 2002 with the Microsoft Office XP Pack for Tablet PC allows you to insert your handwriting into a document and shows you the results of converting the handwriting to text.
Currently, only a few applications have this highest level of pen integration, but many more are in development. In this case, you can edit, format, and even search the ink you created.