...All three are HTML document display components:
THtmlViewer
* The basic component.
* THtmlViewer displays single (non-frame) documents.
* It also forms the basis for the other two components.
TFrameViewer
* Displays both frame and single HTML documents.
* TFrameViewer is oriented more for local file system use.
TFrameBrowser
* Also displays frame and single HTML documents.
* TFrameBrower is oriented for use with local file systems and toward Internet style protocols and URL usage.
* Additional code and/or components are generally required to get data from other sources than the local file system.
...