In the UI it can be good to have different "group of things" that can be good to display and aggregate.
Some will want to show some geographic dispatch, other want a technical view, other business elements.
So with the entities, we can have :
* realm and poller_tag : geographic separation
* hostgroups/servicegroups : technical ones
* template : technical one too
So in a dashboard, the user can choose between "entities" to show and agregate (worse state, importance, etc).