According to Quantum Physics, Physical information is never lost, but according to general relativity & no-hair theorem, that information that enters in a Black Hole is lost Forever (that the physical information of anybody that enters in a black hole disappears, allowing many physical states to transforms into the same state.). This contradiction is known as the Black Hole Information Paradox.
This Voilates the core concept of Modern Physics, that information can never be destroyed.
For e.g., According to Quantum Mechanics, theortically you can recreate the destroyed object, from the information of that object. (This is what we called Conservation of Information).
But that priciple of Quantum Mechanics is not apply, in Black Hole.
After coming up with the concept of Hawking Radiation, the mass of the Black Hole is slowly losing its mass ( Black Hole is Evaporating), and at last, it leaves the only radiation (No matter what body goes inside the black hole), it only ends up with the evaporating radiation.