A 3D interchange format, originally from Autodesk, widely used to move geometry, materials, and animation between BIM tools and real-time visualization/game engines. Revit can export directly to FBX, which is the format most visualization and game-engine tools (like Unreal Engine or Twinmotion in some pipelines) expect as input - useful when a model needs to go beyond a still rendering into an interactive walkthrough or VR experience.