if it's really really black like tar road (tarry black stool), it indicates bleeding.

I once had it. It was really really really black like charcoal.

It's not even those darkish black brown. It's really really black like charcoal. I got really scared.

Then I remember I ate an entire loaf of charcoal bread like two days earlier. Then after that, no more tarry black stool.

So, either u ate something charcoal-based or it indicates bleeding in the GI tract.