Noob question

Im new to macs and have a question:

1. I love how a folder Icon can double as the icon to launch the actual program, with contents within. How do I make existing folders become the launch icon, as some applications already are?

When I go into my applications folder, I can click, for example, GarageBand and it launches GarageBand. If I want to access its support files, though I can ctrl-click it and choose "Show Package Contents." I'd like all my applications to act that way. As it stands now, most of my programs are rooted deeper in applications folder.

that is how all application are in os x. every app is really a package with the actual app in contents/macOS. this is the file thats run if you double click. so thats where you have to point if you want to run something from the terminal. if you want a folder to run an app, you would have to write a folder action apple script.