Intended to keep your phone waterproof, but also so you can use the touchscreen through the transparent lid, recharge your phone, and use the camera. Padded interior.
I think it might’ve been designed for an iPhone 8 because dimensions of 2 5/8 inches wide (2.625") and 5 1/2 inches tall (5.5") so it could fit another phone within those dimensions if not too thick, but functionality might be limited