Help Balloons
Your application can provide help balloons for elements such as menus, dialog boxes, or the content area of a window. The chapter "Help Manager" in Inside Macintosh: More Macintosh Toolbox describes how your application can provide help balloons. You can also create help balloons for some elements of your application's interface--such as its menus--using the application BalloonWriter, which is available from APDA.