A filter group can contain a lot of filters. If you have a lot of products and want users to have the ability to narrow down their selections by filter values, this useful feature is for you. In other words, keeping filters organized in groups gives desired product results. This feature is built in and used the same way in all of the themes. The Flash Search application provides three types of filter groups for the corresponding pages are collection pages, search results page, and specific collection.
Default collections filter group is applied to both collections and search results. It is created automatically based on existing product data, like availability, price, variant options, and more. In case if you want to set up a filter group for specific collections, these collections will display this particular filter group instead of Default. Please note that Default collections filter group cannot be deleted nor disabled but allows you edit the filter options or remove/add new filters to the group.
If you want to custom the filters on search results page you need to enable the "Search filter group". If this option is enabled the search results page will display that filter group instead Default. Otherwise, it will display the default collections filter group. The Search filter group not allowed delete but it allows to turn on and off at any time.
As you know that the default filter group is implemented for product filtering on all Collection pages. In some case you want have different filter groups for specific collections so you can create your new filter group. This new one will be applied to specific collections instead of default filter group. This filter group type can be deleted or disabled anytime and allows you edit the filters or remove/add new filters.