- While using a web browser you need to use calculator.
- Press the Sub-Launcher's trigger to switch to your favourite launcher.
- Launch calculator as usually, and do your calculations.
- Return to web browser whose state remains totally unchanged!
Without Sub-Launcher you had to quit web browser, switch to calculator, and then launch web browser again. This caused web pages to load again, or worse: same data submitted twice to the server.
With Sub-Launcher you can use your favourite launcher to sub-launch any application - the web browser & calculator combination is just an example here.