Worldbuilding is the hobby of creating a fictional world. There's no limit to content when worldbuilding: you might create a realistic world, fantasy world, sci-fi world (or universe!), or any genre possible. You might strive for scientific accuracy, be it geographic, anthropologic, technologic, etc., or you might create your own fantastic settings with strange magics, speculative species, and mystical physics. You might draw maps, write histories, or sketch characters. You might create the world for a novel, or a game, or just for the fun of creating.
If you're posting with the #worldbuilding tag, you might ask a question about proper science ("Can you please find geographic errors in my map?"), or you might ask for a critique on some of your world's lore ("I wrote some history of the reign of King Ludefisk; is it interesting? Do the motivations make sense?"), or you might collaborate and ask for ideas ("I want to create a magic system based on time, how could hourglasses and sundials affect my magic?"). You might even ask more meta-technical questions ("I'm thinking of making a wiki for my world; what are some advantages and disadvantages? What else do you recommend?" or "What software do you use to create old-looking maps?"). Or you might post a link to your world just to share. You might even post a worldbuilding prompt to spark the imagination of other hubskiers ("Describe the religious systems of your world." or "What's a good place to eat in your world?"); these in particular can really show off all the ways people can run with a single topic, and fire the imagination with unique spins; such prompts can also get someone started creating a new world or delving into a new aspect of their world they'd never considered.
Worldbuilding is also closely related to conlanging (constructing languages, like Tolkien's elvish languages or Star Trek's Klingon language), so those who enjoy creating their own languages and writing systems would also find a home with #worldbuilding.
The criss-crossing of tags is nearly endless; you might have written a song that a bard of your world might sing to share with #hubskioriginalmusicclub; you might have made a player's manual for the tabletop RPG you've created for your world and you might share with #boardgames; you might have written a story for your world you might share with #shortstory.
Worldbuilding is thoroughly enjoyable creative hobby, and everyone seems to have a unique vision and method of doing things. Some people work on a single world for their entire life, digging deep into every little aspect one can possibly imagine, and then some. Others (like me) work on multiple worlds at the same time. Others just find the idea intriguing and want to learn where to start (my stock answer is always "Anywhere you please!"). I think this is a wonderful topic for Hubski because it offers lengthy discussion and of course encourages personal content.
So if you're a worldbuilder or have an interest in worldbuilding, I hope Hubski can be a place where you can share your hobby, collaborate, and create.
Bazillion apologies if there's something just like this already; I am #newtohubski and thoroughly over-zealous and energetic when I discover something new and awesome, and my somewhat-casual glance at the tags list yielded nothing. #world seems to be for real world stuff like news, culture, etc., but not fictional worlds.