text: what is blackhole ?   think of a massive star that collapses into a point of singularity due to it's own gravity.  once the radius of the star has shrunk to below the schwarzchild radius r = 2gm/c^2, the star is a black hole.  to give you and idea of how dense that is you would have to fit 11% of the entire earth's mass into a 1 cubic meter box for it to become a black hole.  once this happens, no information can be receive from within the event horizon.  the event horizon is like launching a baseball high in the air.  if you launch it high enough the ball will be able to break free of the earths gravity.  that distance that the ball has to reach to break from the earth's gravity is like a black hole's event horizon.  except that nothing gets past the event horizon, even light.  i'm not sure if it is accept of if it is still debated, but i have heard many times that our galaxy has a black hole at the center and than eventually, all of the stars will be eventually (many billions of years) sucked into it.