Context-sensitive help enables users to obtain help that is directly relevant to a specific program feature or the task they are currently performing. It can make it much easier for users to learn how to use your application because they get information about what they are trying to do while they are trying to do it. This makes your users happier and saves you time and money by reducing the amount of support you have to provide.
There are basically three kinds of context-sensitive help that you need to think about as a help author:
•The user presses F1 and the help is displayed with a topic relevant to the "context" in which the user pressed the key. For example, pressing F1 in an editor could display a topic on editing, pressing F1 in a configuration dialog could display a topic on the features of that dialog, and so on.
•Clicking on a "Help" button in a dialog displays a help topic describing that dialog.
•Right-clicking on a control in an application and selecting What's This? displays a popup window with a text describing the control and what it is for.
•Clicking on any other kind of control in an application (an icon etc.) to display a small popup directly in the application.
The first two kinds of context-sensitive help are implemented with normal calls to specific topics in your help. These are almost always ordinary topics that are included in the Table of Contents (TOC). As the help author you only have to make sure that relevant topics are available, and you must also coordinate with the programmers on the topic IDs and/or help context numbers that are to be used to access the topics from the application. See About implementing context help for some more background information on this.
Context-sensitive help using popup topics displayed directly in your application is a special case. These popups are referred to as "field-level" popups and they are only supported in the Microsoft HTML Help (CHM) format. See About field-level popups in this chapter for details.
Context-Sensitive Help (HowTo)