PADI Touch an interactive manual – it is downloaded to your device, and you work through it in much the same way as you would with a paper manual. You do not need to be connected to the internet to use Touch (although you do need an internet connection to download it initially, of course). Touch also includes the videos which would traditionally have been viewed in the dive centre.
The knowledge reviews can be completed through Touch if you do connect to the internet, otherwise they can be completed at the dive centre. The final exam must be completed at the dive centre. The Touch manual will always be accessible for review in the future, and will automatically be updated as the course content gets renewed.
You can download Touch through the PADI Library app, which is available in the Apple Store or Google Play.