This feature enables the object to detect particles such as those generated by a Fountain effect. Then, whenever a particle encounters this object, the particle bounces off its surface.
If this box is not checked, particles pass through the object.
Items appearing in this list include things such as: One-sided, End caps, or Filled checkboxes, Corner radius or Inner Radius (2-D objects), Radius of Influence (Metaballs), etc.
It is important to note that if the Base Properties of a group or shape is "open" (turned down), the individual components of the group or shape can be individually selected and manipulated.
This can be an extremely useful feature and makes editing much easier, without having to ungroup first. But be sure to close the Base Properties list in the Project window when you're finished editing, or you may end up editing the components of the group unintentionally.
You can also edit any of the Object Properties of an object. These include items such as: Scale, Rotation, Position, Offset, Link nodes, Cycle attributes, Complexity, etc.
Only properties that apply to the object appear in the Base Properties or Object Properties fields. For example, if the origin point of an object has never been moved, Offset will not appear under the Object Properties. Once you move the origin point, however, the Offset entry is added, and the object's position, relative to the origin point, appears here.