You should use subfiltering when you want to create layers of filters in order to display a particular view of project data in a model or drawing.
For example, if you want to see all components in the equipment discipline that are not in an IWP, you could first apply the discipline filter Equipment to a model. After you apply the filter, the model displays all equipment components. Then, you can apply the IWP filter Components Not in an IWP as a subfilter. The model updates to display equipment components that are not in an IWP.
For more information, see Enable subfiltering.