Filter scope in has the following three options:
Explicit scope is defined when a dashboard or visual sends out parameters to other visuals, and the visuals accepts these parameters in their Filters shelf. This can be enabled at the level of each visual. See, Using parameters with explicit scope.
This is expected to be used sparingly for a small number of visuals in each dashboard that represent a high level look at a metric and that should not be filtered by visible filters.
The scope of Click behavior is explicit.
Dataset scope filter applies to all visuals in a dashboard that do not have explicit scope turned on. Filters with dataset scope apply to all visuals in the dashboard that are using the same dataset. This is the default for new filters.
App scope automatically filters all dashboards in the app.