Some applications, don't actually exit when closing them. Instead, they keep on running the background. Applications known for this are
When in this state, trying to restore them by clicking the (non-running) icon on the taskbar often takes multiple seconds, but clicking on the small system tray icon restores them almost instantly. Why is this?
The system tray
Best Answer
When you click on the taskbar icon, the application first has to start and then checks, if another process of the program is running. If so, it puts the process in the foreground and terminates itself.
But when clicking on the small system tray icon, you already have an associated process, which will then get put in the foreground. No application or program tries to start in this case.