Can you tell me anything about Stephen Hawking?
Stephen Hawking was a seminal figure in the science world, very well-known. As an English theoretical physicist, cosmologist, and author/director of research at the Centre for Theoretical Cosmology at the University of Cambridge, his life was science. 
You said he was an author. Can you tell me which books he wrote?
One of his most popular works was a book called The Grand Design, where he paired with Loenard Mlodinow, published in 2010. This work examined the history of scientific knowledge about the universe and explained the 11 dimension M-theory, and also stated that a Unified Field Theory, proposed by Einstein, didn't exist! 
Can you tell me anything else about his discoveries or theories?
So, Hawking was the first person in history to put into the world a theory of cosmology that was underpinned by a union of general theory of relatively and quantum mechanics. What's more, he was a huge supporter of the many-worlds interpretation of quantum mechanics, and it was a large part of his work.
I know nothing about quantum mechanics. Can you tell me something else about that?
Quantum mechanics
Quantum mechanics (QM; also known as quantum physics, quantum theory, the wave mechanical model, or matrix mechanics), including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles.
Classical physics, the physics existing before quantum mechanics, describes nature at ordinary (macroscopic) scale. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale.
Quantum mechanics differs
Stephen Hawking
Stephen William Hawking (8 January 1942 – 14 March 2018) was an English theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge at the time of his death. He was the Lucasian Professor of Mathematics at the University of Cambridge between 1979 and 2009.
His scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity and the theoretical prediction that black holes emit radiation, often called Hawking radiation.