WinHelp: Context-Sensitive Help for Your Programs
An application can offer user help at just the point in your interface when users will need it.
You can also view the .hlp file created for your project with the WINHLP32 utility (issue winhlp32 file.hlp from the command line).
For more information on context-sensitive help, see the following Knowledge Base articles (search for the article number online, in the MSDN Library Visual Studio documentation, with Search titles only cleared.):
Q244232 : HOWTO: Add Context Help Button (? Button) to Title Bar of CPropertySheet
Q141724 : Context-Sensitive Help in a CDialog Object
Q167698 : Help95.exe Implements Windows 95 Style Help
Q149343 : Implement Context-Sensitive Help for Dialog Controls