Who is Stephen Hawking from A Brief History of Time and what is their importance?

Hawking is the author of the book and an esteemed theoretical physicist. As such, most of the book is about his thinking based on the theories of others and theories that he has developed. His personal life comes through a bit when he mentions his disability, but more importantly he adds passages about his professional life, which includes being a consultant to the Vatican regarding the nature of the universe and giving lectures around the globe.