Pay-per-Day insurance uses your phone's location to work out when you're abroad and where you're in the world, and charge you accordingly for those specific days and regions.
To do this you need to turn on location services so we can know when you go abroad and where you travel. You will be notified when you are covered.
The price you will be charged for each location is made clear as you buy the policy from the 'Insurance' section of your app. If you travel a lot, don't worry, there's a cap on how much you will be charged in a year.