English term (edited): app onboarding pages

Mobile app onboarding is the process of getting new users to understand and engage with your app enough to keep using it, instead of abandoning it after the first use.
https://medium.com/@the_manifest/6-user-onboarding-flows-for...

Refer to the following animation video for illustration:

https://www.youtube.com/watch?v=nRG3wWeMqAQ


Mobile app onboarding best practices
In his brilliant article on Smashing Magazine, Alon Even provides a list of 3 simple guidelines that need to be adhered to so as to ensure a great onboarding process.

These are:

Give an overview: This can be achieved by highlighting the important areas of the app while keeping the app screen itself visible. In this way users would be able to easily locate the functionality they are looking for.
Show the value: Show the key strengths of your app by utilizing as few screens as possible during the onboarding process. Then proceed to engage them further after you have brought them onboard.
Show what they need to do to get to the next step: Guide your users step by step (or screen by screen for all that matters), thus providing a smooth onboarding experience.
https://usabilitygeek.com/mobile-app-onboarding-how-to-do-it...

User onboarding is the process of setting up first-time users to be successful with your product.
https://apptimize.com/blog/2016/04/ultimate-guide-user-onboa...