FrontEndExecute[expr] sends expr to be executed by the Mathematica front end.
FrontEndExecute[expr] sends expr to $FrontEnd via MathLink using LinkWrite.
The standard Mathematica front end can handle only specific notebook manipulation commands such as NotebookApply, NotebookLocate and SelectedNotebook. It uses the versions of these commands in the FrontEnd` context.
FrontEndExecute[FrontEndToken["name"]] executes named commands in the front end, typically corresponding to menu items.