The HtmlEditor is a C# wrapper for Microsoft's Mshtml COM component. Mshtml is the part of Internet Explorer which renders HTML. It also has an edit mode which makes it relatively easy to create a GUI editor that generates HTML. Since it is a .NET assembly, the HtmlEditor can also be used with Visual Basic .NET or any .NET language. However, because it invokes a native Windows DLL it will not work with Mono or other .NET implementations on Linux or the Mac. The HtmlEditor is presented as a sample: it is free for both commercial and non-commercial use.
Visual Studio .NET also supports using Internet Explorer as an ActiveX control. This is also a viable approach, and probably better if you want to embed a web browser in your application. However, some people have run into problems with the ActiveX control, and the HtmlEditor is easier to customise. If you want to display and/or edit HTML, the HtmlEditor may be a better solution.test and it is a smaller footprint too.
Useful links for working with Mshtml
Alternatives to the HtmlEditor
Programming Techniques to help you work with the HtmlEditor
Reference to properties, methods and events
Frequently asked questions about the HtmlEditor