Ghost objects have nothing except a collider and are absolutely penetrable. They are used to detect collisions with other physical objects. When a collision is detected, it will trigger a certain event or behavior of certain objects or the environment. You can think of a ghost object as a sensor that performs a certain task when other objects collide with it. For example, you can make a door open when your character collides with a ghost object in front of it. Ghost objects can also be used on top of dynamic objects to ensure a more realistic visual interaction between objects.
To make an object a ghost object, select an object in a scene in the Edit mode, go to the Physics tab in the Inspector panel, and turn the Physics on. Change the type of the Rigidbody to Ghost. In the example below, you can see the Physics tab with the settings for a ghost box object.
You can apply the Ghost rigidbody type to any primitive available in MANU and any imported 3D model.