Continuum is the key that makes it all work. It is the underlying feature that turns your phone into a PC and more importantly, a big-time productivity tool. It works seamlessly with the apps on your phone, giving them the ability to take advantage of a larger second screen. It could also be customized to fit your preferences, much like you would with your Windows 10 PC.
Even when you're connected to a display or monitor, you can still use your phone in all the usual ways – make and receive calls, send messages, and check your social media apps.