Who is John Nash? Why is he renowned?

John Forbes Nash Jr. was a brilliant twentieth-century American mathematician. He won two of the field's top international awards, the Nobel Prize in Economics and the Abel Prize for his work on game theory and nonlinear differential equations. He came up with one of the fundamental concepts of game theory, known as the Nash equilibrium. He also made outstanding contributions to the analytical logic of advanced mathematical theory.
Nash's personal life story also contributed widely to his renown. While working at the Massachusetts Institute of Technology in the late 1950s, he became severely mentally ill; he experienced delusions that he was being secretly monitored and persecuted. He was diagnosed with paranoid schizophrenia. Over a period of years, he returned to sufficient mental stability to resume his studies and teaching. His life story was recorded in the book A Beautiful Mind by Sylvia Nasar. The Hollywood adaptation of Nasar's biography, released in 2001 and starring Russell Crowe as Nash, won four Oscars including Best Picture. Nash and his wife died in an automobile crash in 2015.