"Launch" - I believe this refers to LabVIEW starting. If you're running an executable, it would be when that executable is opened.
"Open" - This is when a specific VI (or control, though there're not many things that happen when a control is opened) is started (double click on it in a project or in a file system folder), and you can see its front panel on your user-interface.
"Call" - When something is executed from the block diagram of another executing VI.
"Loaded" - Things are loaded into memory at different times. Anything in the direct hierarchy of a VI is loaded when that VI is opened and loaded (If you open "Main", it and all of its sub-vis and their dependents will be loaded into memory). For dynamically loaded VIs, when the code which loads the VI (not runs) executes, it is loaded into memory.
I hope this clears up any confusion.