Play framework concepts

Could someone explain how the web apps work on play framework example? The things I misunderstand: 1)Which part of the code(I mean code from examples listed on play framework site) allows many users to use the same app at same time? 2)For example I have a program : a textField, button and list. Write in textfield, press button and the text is added to the list. Every user should have own list, but where should I store the data if it's objects, in memory? In DB? In session/cookies? And how this data should be recognized, by session of? Are there any good examples?