A black hole bends space so tightly that if light gets too close (the event horizon), it gets sucked in. That's why we refer to it as a hole.
This still doesn't make sense to a non-physicist like me. You haven't explained why the photon can't just go into the curved area of space and straight out the other side.
Any sufficiently advanced bug is indistinguishable from a feature. -- Rich Kulawiec