It is possible to  hide apps on iPhones  in multiple ways. For example, you can
organize them in folders or place them in your app library. When you have iOS
14 or later installed, you can also remove all home screen pages in order to
reduce clutter on your home screen. 

Suppose
you need to locate an app you haven’t used for a while and don’t remember how
to access it. There may be  hidden
apps  on someone else’s phone that
you need to check.   Learn here: https://www.soldrit.com/blog/how-to-open-hidden-apps-on-iphone/