Ben Lovejoy, 9to5Mac:

We’ve heard reports before that Apple plans to include a periscope lens on future iPhones, and a new Ming-Chi Kuo report today suggests this is coming in 2022.

Rumor aside, the focus of the linked article is this:

What exactly is a periscope lens, and what would it mean for future iPhones?

A typical iPhone lens stacks its elements perpendicularly away from the iPhone. That lens stack is what makes the camera bump in the iPhone case.

A periscope lens uses a mirror to let the stack of lens elements live inside the case, with optical zoom without a camera bump made possible by sacrificing interior space.

Ben does a great job explaining all this. Great read.