Layered navigation Filterable (with results):

– This attribute will be shown only if there are products matching any of its attributes-options value.
– filter is shown on the category page Layered Navigation. However only options values, where products are available will be listed for the filter.
– In this case, products list filtration works if selected filters change from currently shown options.

Layered navigation Filterable (no results):

– In this case, All attribute options will be shown even if there won’t be any products matching or associated with them.
– filter is shown on the category page Layered Navigation. if the filter is set to ‘no results’, it will list all options, even no products are associated with specific options.
– If any attribute options not Associated with any products then its show Zero counts. Ex: Color Attribute with options Red (0).

For more understanding, you can check these options from admin and check the difference in the front end to get a better idea.

Thanks!