last science nerd contribution for posterity.
artists rendition of a black hole and relevant defintions. done well before they photographed one last week. notice rendition kinda looks like the photograph
cross section:
The "singularity" .. infinitely small, infinitely dense, infinite gravity. "Infinity" in the math/noun sense -- not an adjective. There is no space, no time, nothing at all we can seem to comprehend. Also, note some scientists think its all a buncha BS -- singularities and the like -- but that's another story and I am not smart enough to sort it out.
The event horizon is the boundary where light cannot escape because of the infinite gravity of the singularity. It looks "black" because NO LIGHT (or any electro-magnetic radition at all) can escape the gravity of the singularity.
As such, nobody knows what's happening INSIDE the diameter of the event horizon .. except that when stuff crosses the event horizon (a star, galactic gas cloud, another black hole gets sucked in), it makes the black hole more massive (some are billions of times more massive than our Sun, like M87).
That in turn increases the diameter of the event horizon .. the black hole got physically "bigger" after it "ate" stuff.
Enough of that .. gotta bus to work on