backgrounder

[ bak-groun-der ]
/ ˈbækˌgraʊn dər /

noun

a briefing for the press in which an official, often from government or business, gives background information to clarify particular policies, actions, or newsworthy issues, with the understanding that the official will not be named or quoted directly in any resulting press reports.
any briefing or report for the purpose of providing background information.

Origin of backgrounder

An Americanism dating back to 1955–60; background + -er1