HTML Help:

This is currently the most popular electronic help format for Windows applications. It packs your entire help project into a single CHM file. Fast, compact, excellent navigation and usability, universally compatible and full interaction with applications. Displayed by the HTML Help Viewer, that has been included with Windows since Windows 98.

Webhelp:

Displays in normal web browsers on all platforms (Windows, Linux, Mac OS X, Unix). An emulation of the HTML Help interface, designed for use on the Web and intranets. Complete with a dynamic Table of Contents pane, keyword index and full-text search. Consists of a directory containing a large number of HTML files, graphics files and the files needed to display the Table of Contents etc.

eBooks:

This proprietary Help & Manual format packs your entire project into a single executable file with an integrated viewer program that can be displayed on any Windows computer, from Windows 95 and above without any additional software. This format also provides an emulation of the familiar HTML Help Viewer layout so that all users will be able to use it intuitively without additional explanation.

Adobe PDF:

Your project can also be output as a fully-formatted and full-featured PDF file that can be displayed on any computer with a PDF reader. Ideal for providing manuals that users can print themselves, either on CDs or for download.

Printed manuals:

The Print Manual feature (in the Application Menu) generates a temporary PDF file in the background and outputs it to your printer. Also supports booklet format (multiple pages per sheet) and duplex printing.

MS Word RTF:

Old print-style format, support is provided for backward compatibility. Outputs your project to an MS Word Rich Text Format RTF file. Many dynamic help features are not supported, minimum options.

Visual Studio Help:

This special format is also known as MS Help 2.0. It is provided for programmers who need to use MS Help 2.0 to document projects in Visual Studio .NET. It is not documented extensively in the help because Microsoft has not released it for general use under Windows. This format is irrelevant for normal application documentation.

For details see Visual Studio Help in the More Advanced Procedures section and the documentation of the MS Visual Studio .NET package. (If you don't have this package you don't need and cannot use Visual Studio Help.)

Winhelp:

The predecessor of HTML Help, now obsolete and should not be used for new projects, although Help & Manual includes full support for Winhelp for backward compatibility. Not supported in Windows Vista by default. Consists of separate help (HLP) and contents (CNT) files. Not particularly user-friendly, looks and is out of date. Not recommended unless it cannot be avoided.