This document discusses theoretical models used in ordinary research to understand phenomena, and artefactual models used in design research to develop artifacts that control targeted outcomes. Theoretical models use vocabulary, rules, and generalizations to describe and predict behaviors, which are tested against real-world observations. Artefactual models describe how artifacts will behave based on relevant theoretical models and untested assumptions, and are tested through simulations and empirical tests. Both aim to improve models and control the world, with design research focusing on developing useful artifacts.