You can filter the results shown in a visualization with the 'Add Filter button'. You can use this button when exploring a visualization, or when editing a page with a visualization on it.
Filters have different options, depending on what values you are filtering on. Text can be filtered by typing in a value, or by selecting values that occur often. _place_holder;
For numbers, you can select a range to filter on.
Once set, you can click on the 'Configure' link to change the filter type, and to show the filter to viewers of your Silk.
Here is an embed from world.silk.co showing population growth. The Region and Population Growth filters are set to display to all visitors. Use them to filter on a region or zoom in on a specific range of population growth.