Allowing multiple selections
Set whether the customer is able to select more than one item in the filter
No multiple selections
If one option in the filter is selected, and then another one, it stops filtering on the previously selected option.
Yes, narrow the results
Allow multiple selections with very specific results. Once more than one filter is selected, only products that match both of those filters will display.
Yes, expand the results
Any product that matches any of the chosen filters will display.