What is the difference between a filter and a filter control?

A filter is applied by the report author and cannot be changed by the reader — excluding internal traffic, for instance.

A filter control is a component the reader interacts with: a dropdown, list, slider or search box.

Filters can be scoped at chart, group, page, report or data-source level. Data-source level is the strongest, since it applies everywhere and cannot be removed on an individual chart.