What you learned in school
Astronomy textbooks taught that black holes were cosmic vacuum cleaners that completely destroyed all matter and information crossing their event horizons. Students learned that nothing could ever escape and everything was crushed to infinite density at the singularity. Black holes were portrayed as ultimate destructive forces that annihilated anything unfortunate enough to fall into them.
What we know now
Astronomy textbooks taught that black holes were cosmic vacuum cleaners that destroyed all matter and information that crossed their event horizons. Nothing could ever escape, and everything was crushed to infinite density. Stephen Hawking's work showed that black holes actually emit radiation (Hawking radiation) and slowly evaporate over time. They also don't destroy information - it may be encoded on the event horizon. Black holes are more complex objects that follow quantum mechanical principles, not just simple destructive forces.