What happens when two mirrors face each other in a certain angle?

Depending on the angle between them, you will get multiple reflections of any object between the mirrors.

If the mirrors meet at an angle of x degrees, an object placed between them should generate a maximum of (360/n) - 1 images. Parallel mirrors should, on that basis, produce an infinite number of images but because of microscopic flaws in the mirror, absorption, internal refraction etc, the images will degrade more or less exponentially.