https://www.theverge.com/circuitbreaker/2018/10/30/18042548/apple-ipad-pro-usb-c-charge-iphone-adapter

Apple’s just-announced iPad Pros are making the switch to USB-C, and with that switch comes a nifty new feature: you’ll actually be able to use your iPad to charge up your iPhone on the go, making it the world’s most expensive battery pack.

Just plug in your iPhone (or, presumably, any other device that you want to charge up) into the iPad’s USB-C port, and you’ll be able to charge it up. Apple hasn’t said yet what kind of power that iPad will be able to push — you probably won’t be able to charge up another iPad Pro or a Mac, for instance — but if you’re out and about and need some extra juice for your phone, it’s a neat option to have.