Over The Air (OTA) Updates is minor updates being pushed out to your phone when you open apps. For the Camino Ninja App that is usually minor updates to routes, albergues, photos and functionality. Instead of updating automatically every time you open the App, it now automatically updates whenever you are on Wi-Fi and ask if you want to download and install updates when you are on mobile data. This is another data-saving feature. And it also makes sure you always have the latest updates, if you choose to.
You also have the option to check manually for updates.
Enjoy, and Buen Camino!