What spins as a black hole? (lame question) Obviously I am not a physicist.
I have seen What is black hole spin?
but this is not what puzzles me.
If I understand correctly, black hole has only three features (please correct me):

*

*angular momentum, i.e. spin.

*charge

*mass

My problem is to understand what spins.
The matter that might spin is disconnected from Schwarzschild radius due to limit of the light speed.
Schwarzschild radius in another hand, is the mathematical concept, it doesn't spin, does it?
So please could you explain WHAT spins exactly?
EDIT: I see that my question was corrected so "angular momentum, i.e" is added but angular momentum of what?
 A: My two cents of the euro.
Lets take a specific observation of black holes the LIGO merger,seen here .
The video is a complicated solution from the data gathered with the experiment, but rotation is detected. It is an animation using the data.
What is rotating? The background stars to the event are distorted through the distorted space-time and thus the motion of the two black holes can be detected/calculated.
A spinning black hole will be changing the spacetime about it and it is the distortions in the background that show it off. If it is at rest with the background stars there would be no motion of the images. From conservation of angular momentum, it must be the rotating black hole that is creating the rotary motion of the images, so the black hole is assigned a spin.

but angular momentum of what?

At the level of general relativity, where the singularity is modeled as a point it is useless to model a spinning superheavy point. If/when gravity is quantized the singularity will disappear and become a fuzzy region as the one imagined for the beginning of the universe, where all the mass will be in a volume defined by a probability space-time region, where a spin with respect with the background starts can be assigned/measured.
