A world model in artificial intelligence is a machine learning system that builds an internal representation of an environment. Often this is via understanding objects within video, which predictive LLMs cannot. The model predicts how that environment changes over time in response to actions. Researchers design world models to help agents plan, reason, and act without constant real-world trial and error. World models differ from systems that merely classify or generate outputs. They simulate dynamics such as physics, object interactions, and causality. Early ideas date to the 1990s. Modern versions power robots, autonomous driving, and interactive video generation.