A filtered view represents "a view on top of another view", which can be used to filter (include or exclude) specific elements and/or relationships, based upon their tag. In summary, you create a view with all of the elements and relationships that you want to show, and then create one or more filtered views on top, specifying the tags that you'd like to include or exclude. The benefit of using filtered views is that element and relationship positions are shared between the filtered views.
Filtered views can be created on top of static views only; i.e. System Landscape, System Context, Container and Component views.
A typical usage scenario is something like showing the current state vs future state. Here we might define a single System Landscape view, with two filtered views on top; one showing the current state, and the other showing future state.
Current state: User uses Software System A for tasks 1 and 2.
Future state: Software System B will be introduced in the future to fulfil task 2.