Online Help is topic, procedural or reference information delivered through computer software. It is a form of User Assistance. Most Help is designed to give assistance in the use of a software application or operating system, but can also be used to present information on a broad range of subjects. When Help is linked to the state of application (what user is doing), it's called context-sensitive Help.

Online Help is created through Help authoring tools. It is delivered in a wide variety of formats, some proprietary and some open-standard, including:

Hypertext Markup Language (HTML), which includes HTML Help, HTML-based Help, JavaHelp, and Oracle Help.

Adobe Portable Document Format (PDF)

Microsoft Help Platforms

Microsoft develops the platforms for delivering Help systems in the Microsoft Windows operating system.

Microsoft QuickHelp - Ralph Walden joined Microsoft in 1987 and wrote an online help system for MS-DOS and OS/2 called QuickHelp. Ralph was also primarily responsible for WinHelp and HTML Help 1.x.

Microsoft WinHelp (.HLP) - Based on Rich Text Format, this was the industry standard for Windows 3.1 and Windows 95/NT. The popular Windows Help program (WinHlp32.exe) was included with all Windows operating systems from Windows 3.0 until the Windows XP operating system. However, the Help engine will not be included with Windows Vista and will only be available via download. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnlong/html/AppComp.asp (click Help Engine Support)

Microsoft Compressed HTML Help (.CHM) - Based on compiled HTML and other data such as images and JavaScript. In 2006, this is the current standard available from Microsoft as HTML Help 1.4. Originally, HTML Help 1.0 was released in 1997.

HTML Help 2.0 - In 2001, Microsoft announced plans for a wide release of HTML Help 2.0. This platform was developed by Microsoft and shipped in 2002 as the help format for Visual Studio .NET, MSDN Library and Technet products; however Microsoft announced it had cancelled plans to make the format publicly available.

AP Help 1.0 - Assistance Platform Help is the new generation of online Help being developed for and shipped with Windows Vista. It will not be made publicly available as an authoring platform for other software vendors. It will be used by Microsoft, OEMs, and certain corporations.

AP Help 2.0 - This version of the new Assistance Platform Help engine is currently on hold.

Other Platforms

Apple Help (.HELP) - Apple Computer's proprietary help platform for the Mac OS 8.5+ operating system.

Sun JavaHelp (.js) - A platform-independent help system written in Java programming language by Sun Microsystems. It runs on any platform and browser that supports the Java Runtime Environment (JRE). http://java.sun.com/products/javahelp/

Oracle Help - Two formats developed by the Oracle Corporation: Oracle Help for Java (OHJ) and Oracle Help for Web (OHW). http://www.oracle.com/technology/tech/java/help/index.html

DotNetHelp - A new Windows Help format, designed to replace the .chm format, that also supports .NET applications.

The Texinfo program and format (also known as the "info" system) is the official documentation system for the GNU project.

Unix man pages are the standard method used to document Unix commands.

Information Presentation Facility (IPF) is the help system used by IBM's OS/2 system.