Key Bindings

The association between a command and the key combinations that should invoke the command is called a key binding.  Plug-ins can define key bindings along with commands in the org.eclipse.ui.bindings extension point.

...
      <key commandId="org.eclipse.ui.file.save"
            contextId="org.eclipse.ui.contexts.window"
            schemeId="org.eclipse.ui.examples.contributions.scheme"
            sequence="CTRL+S">
      </key>
...

There is our friend org.eclipse.ui.file.save. In Eclipse, the workbench registers the SaveAction as a handler for this command id in every Workbench Window.

The sequence attribute for a key binding defines the key combination that is used to invoke a command.  When the workbench SaveAction is active, the key combination CTRL+S will invoke it, since the workbench uses the same command id for its SaveAction.