Nash Equilibrium is a concept in game theory where players in a strategic situation choose their best possible strategy, given the strategies chosen by others. In this state, no player can benefit by changing their strategy while the other players keep theirs unchanged. This means that each player's decision is optimal, considering the choices of others. In simpler terms, imagine a group of friends deciding where to eat. If everyone picks a restaurant that they like, and no one wants to change their choice because it would make them worse off, they have reached a Nash Equilibrium. This helps explain how individuals make decisions in competitive situations.