Game theory is a model in which the different "players" have a limited set of "moves" to choose from, and that by pairing each of player 1's moves which each of player 2's moves you can create a "payoff matrix" which shows the outcome for both players for each pair of actions.
Traditionally, game theory assumes perfect knowledge of the payoff martix, whic can be problematic for the theory, but usefull to a player in a situation of imperfect knowledge.
The game can either be sequential (player 1 goes first, player 2 knows the move before making their own), or simultaneous (both players must choose a move before either is seen). The real world exists as an ongoing conversation with a combination of both types of games (see also Meta-Game Theory).
In terms of activism, the players could be considered "Resistance" and "Power", so for a given act of resistance, a form of power will have various choices in how to respond. The form of power can be a person, a company, a governement, a political party or a system (see also Systems).
For example, if a popular revolt occurs under a dictatorship, the players are the leaders of the resistance (if it has leaders), and the dictator. If the people take to the streets, the dictator can choose to let them protest freely, limit their access to geographical areas/media coverage, violently repress the demonstration, or attack the resistance's base of support. The choices of the dictator are limited by a number of factors: Are they dependent on the support of other goverments or institutions which would not approve of a given "move"? Does the dictator have the means to violently repress the demonstration if he wanted to?