The "Starter" window can be used to start additional tools and to open documents directly from within Flight Simulator.
The items to be started can be grouped in a tree. By right-clicking in the tree you can open a menu that contains all available options, also available as toolbar buttons:
Starts the selected item (also: double-click).
What happens when "starting" an item depends on the type of the item. An application (*.exe) is started, a document (*.pdf, *.html, *.txt) is opened etc. In fact, the same thing happens as when double-clicking the item in an Explorer window.
Change the description of the selected item.
Adds a new group.
Adds one or more items to be started.
Deletes the selected item.
Moves the selected item up or down