On-line Help provides small packets of information to help users where and when they need it, in a logical and structured manner. Users should be able to quickly find useful and relevant information. The most widely used Help formats are WinHelp, HTML Help and WebHelp.
WinHelp - WinHelp is short for Windows Help. It's the original compiled Help format. You can use WinHelp if your audience uses a Microsoft Windows operating system – Windows 3.1, 95, 98, NT 4, NT 5 or Windows 2000. Every version of Windows automatically comes with a built-in WinHelp viewer.
HTML Help - Help systems for Windows 98 and Windows NT use the Microsoft HTML Help format. Microsoft HTML Help can be viewed on Windows 95 and NT 4 using Internet Explorer 4 or later. Instead of using the WinHelp viewer, Microsoft HTML Help uses an Internet browser (specifically Internet Explorer 4 or later) as its Help viewer and displays Help in a tri-pane HTML Help window.
WebHelp - WebHelp is a cross-platform Help. This format runs on multiple platforms (Windows, Macintosh, and Unix) and can be viewed using a variety of browsers, including Netscape Navigator and Internet Explorer.
JavaHelp - JavaHelp, developed by Sun Microsystems, is a compressed output type designed to work with applications written in the Java programming language. JavaHelp and Java applications run on a variety of platforms (Windows, UNIX, Mac, Linux, etc.).
As technology advances other Help formats are emerging. For example, Windows CE Help is another Help format that runs on palmtop computers and other hand-held electronic devices.