A Standalone AssetBundle is an archive file bundled in unity for the PC Platform (HoloLens Device) that contains your unity scene for Fectar Studio. It contains non-code assets like your Models, Textures, Prefabs, Audio clips and Animations.
A Standalone AssetBundle has to be added to the Unity3D Spot in Fectar Studio to view the space as a Mixed Reality Experience on HoloLens using the Fectar App.