John Nash was educated at both Bachelor and Masters level in mathematics at Carnegie Institute of Technology. He went on to Princeton University to work towards his doctorate, which he completed in 1950 with the publication of his Non-cooperative Games thesis in which he laid down the mathematical foundations of game theory (brought to popular culture in the film A Beautiful Mind).
In mathematics, game theory looks at situations where two (or more) participants have a range of possible choices that they can take. Each decides which choice to make in the light of others' choices, since the outcome is produced by the particular combination of their choices.
The Nash Equilibrium is the outcome which would be produced by each making the best choice, given their knowledge of others' choices.
One of the classic examples of games theory is the Prisoner’s Dilemma. Discover this for yourself with The Open University's interactive version of the Prisoner's Dilemma.
John Nash died in a road accident on May 23, 2015. You can read an obituary on The Economist website.