Before the first session there is a document that lives only in the game master’s head: what the world is like, where it begins, who wants what. This is that document on one A4 page, written to be handed to the players. It holds nothing they are not meant to know.
A pitch in a line, in the heading. Under it the truths about the world — two to six things every character would know — and the place where the story begins. Then the factions the party can side with or against, each with what it wants and what it offers, a list of reasons a character might be here, the incident that opens the campaign, and the books and films that set the mood.
Concept, aim, tone, the safety tools and the lines and veils belong to the Session Zero Form. The secrets, the dangers and the log belong to the Campaign Tracker, which the players never see.
System neutral, A4 at 300 DPI as a PNG or a PDF, in four looks. The evening that follows from it is a Session Planner.