rounser said:
Rare is the DM who starts "worldbuilding" by designing a CR 1 goblin deadfall somewhere on a 10ft grid map - 99.9% would refer to it as designing an adventure. D&D would probably be a lot more fun if this is where DMs started work, but generally they don't - they start with macro level worldbuilding. They start with goblin migrations, or deciding that there's a nation of goblins with hobgoblin overlords or something, and the encounter-level deadfall may never get made.
I can't speak about what the average DM does; if anything, EN World has taught me that there isn't any hard-and-fast rule about that. What I can do is describe my own method, which I think qualifies as world-building.
My own method is bottom-down, top-up, bottom-down.
I'll start with creating the adventure setting that I want play to begin in. This might mean a dungeon, wilderness encounter tables, a village, whathaveyou. As a result of the choices I am making, I will do some top-down work. I decided I want encounters with tribesmen; who are these tribesmen? I placed some spider-cultists; who do they worship, and why?
From these questions, I create a short player briefing on the area. It might include new options based on my decisions (such as the Lakashi tribesmen in my Lakelands, that came from a desire to run a "tribesmen" encounter). I might create some extra crunchy bits that PCs can play with (Totem Spirits of the Lakashi). When the PCs decide to go from Long Archer (initial setup) to Selby-by-the-Water, I start the process over again.
When working on the first part, I decided that there were "Lake Monsters" (pleisiosaurs) because I liked the Loch Ness image of them. When working Selby from rough to ready, I added "leatherwings" (small pteradactyls) that largely take the place of pigeons and seabirds. This in turn, perforce, makes me think about the place of dinosaurs in my world, and I decided that there are larger, more common reptiles in the warmer south....a detail that piqued the interest of at least a few players.
And so on, and so on. What is done at the "bottom-up" level drives what is done at the "top-down" level, and vice versa.
I've never actually seen anyone approach worldbuilding in a different way, although I am sure that people do.
RC