Mobile Input?

I just saw this now.

Basically, I think it means you have to have previously set up or synced your mobile device using some Unity App that you can download onto your phone, and then when you press Play in the Unity editor to test your game/App, and maybe even run a build of your game/App, you'll need to use the phone to actually play the game.

Presumably this is really only for people who are trying to make a game/App for mobile devices and want to test how the game plays on their phone. But God knows what they felt the need to put it up there as a main tab by default and just convolute the Unity interface even more.