[Gonso]

Questions,

A Nash Equilibria exists in situations where a given player can't improve his EV no matter what he does.

Let's we're playing a game. Player A does does one thing, and the Player B does his thing. If Player C winds up with the same result no matter what action he takes, then there's a NE. Most practical applications today for NE pertain to heads up jam-or-fold situations.

"Mathematics of Poker" covers this a little bit, and there have been a few good threads on it. You could look up the "SAGE system" from a Card Player article that was decent and tied in to this.