Smart view is an app that let's other people view your phone screen. I had to use it when my phone was getting pop ups and I couldn't locate the issue. The tech saw my screen, I assume they can navigate as well because he located the app that was causing the issue and we solved the problem.
Smart view is a way to cast your phone to another compatible device like a tablet or TV. If it is not connected to another device, it is off. If you are not connected to anything, it is actually off, so don't worry about it.
