It is possible to create links to workbench commands in help content. When the user clicks the link, the command will be executed. This feature is similar to Active Help in that it uses JavaScript to bridge between the documentation HTML and the Eclipse Java runtime. Also like Active Help, the command framework is extensible; so you can contribute new commands with interesting behaviors. However, unlike Active Help, there are a large number of useful commands already defined in the workbench and more are being added all the time. This should be appealing to documentation authors because linking to an existing command does not require writing any Java code.
Command links can be used to:
To get an idea of the range of commands available, look at the General > Keys preference page. This page is used to bind key sequences to commands so it shows the list of available commands. Note that not every command will do something useful from help content. Many commands are designed to work within a somewhat narrow context (like a particular view, or expecting a certain type of selection).
If you want to define your own commands, refer to the documentation for the org.eclipse.core.commands API package and the org.eclipse.ui.commands and org.eclipse.ui.handlers extension-points.