The Heisenberg uncertainty principle allows these "virtual" particles and antiparticles to emerge from the vacuum for a brief moment and disappear back to the vacuum again, without violating the energy conservation law.
Through this process the black hole loses mass e to an outside observer it would seem that the black hole has just issued a particle.
This reasoning leads to the conclusion that the black hole radiates an energy, called Hawking radiation (1974) and this loss of energy it brings the black hole to become smaller and smaller and, with time, evaporate.
In this regard the theoretical physicist Leonard Susskind, one of the fathers of string theory and supporter of quantum physics writes: : “Stephen said that when a bit of information falls into a black hole it is permanently lost to the outside, despite the fact that he also proved that black holes evaporate and eventually disappear…. The problem that upset me is that the most basic principle of physics—the principle that underpins everything including classical physics, thermodynamics, quantum mechanics, energy conservation, that physicists have believed for hundreds of years—is that information is never truly lost. It can be scrambled beyond recognition, but it is never completely erased.” [1]
Ethan Siegel/
Starts with a Bang
Hawking radiation as particle pairs are created near a black hole
(Source: University of St Andrews)