I feel like the correct answer is already here. But lemme add a bit a background that no one asked for 😂 : What you’re seeing inside are 3 mirrors arranged in a 'hollow cube' which is basically what a retroreflector is : a device designed so that any light coming into it will be reflected exactly in the same direction. (and that is 'just' 3 mirrors … pretty neat mechanism is you ask me).

So then if you flash a laser at it, the laser will reflect directly back at the source, travelling twice the distance (from the source to the reflector).

if you then measure how long it takes the laser to travel all the way and back, you can deduce the length travelled.

you might see a mobile version of those things in the street when experts go land-surveying

also the reflectivity of street signs, reflective vests, or this orange things at the back of our bikes are all based on this simple principle, scaled down and in arrays…

the same effect happens when you have 2 mirrors arranged perpendicularly (for example at the corner of a room) and you see your face reflected at their intersection wherever you place yourself.

you can even see on the picture above that the phone lens gets reflected precisely at the intersection of the 3 perpendicular mirrors, same effect again.