Welcome to the first iteration of The Dungeon Master’s Guide to Building an RPG Campaign! Roleplaying games come in all shapes, sizes and subgenres, as do the DMs that run them. But a common thread that runs through all of those games and all of those players is the need for a believable and articulated world.
Building a world as the DM is about much more than coming up with a plot for the players to follow. Whereas something like a book or film is linear and has defined plot points, the moment you give players agency in a world you invite variability.