Agent-based modeling is a computer simulation method where agents make decisions based on their interactions with each other and their environment. It combines elements of game theory, complex systems, emergence, computational sociology, multi-agent systems, and evolutionary programming.
From Wikipedia:
An agent-based model (ABM) (also sometimes related to the term multi-agent system or multi-agent simulation) is a class of computational models for simulating the actions and interactions of autonomous agents (both individual or collective entities such as organizations or groups) with a view to assessing their effects on the system as a whole. It combines elements of game theory, complex systems, emergence, computational sociology, multi-agent systems, and evolutionary programming. Monte Carlo Methods are used to introduce randomness. ABMs are also called individual-based models.