We are offering two types of PhonePe flows.
In-App Flow Where the user device has PhonePe application installed. We invoke the Installed PhonePe application to do the payment transaction. User will see the Bottom-sheet(In-app) like below UI on the checkout screen.
Web Flow If the user device doesn't have PhonePe application installed, we will show the Web checkout to make the payment, where the customer can make the payment by logging into the PhonePe and using the available payment methods.
Documentation: https://devguide.payu.in/mobile-sdk-android/phonepe/