Some people hear the term, world building, and shrink away, their eyes averted.
Other people race toward the idea, excitement and ideas brimming over in their minds.
Whether you're writing scifi, fantasy, or another genre, to some degree you must create a world. Outside of the speculative fiction genres, your world will follow a lot of the norms of your story's time period, but world building still applies on a smaller scale. It's constrained by what we know about that time.
With speculative fiction, writers get to create everything. Yes, everything: religion, countries, clothing, manners of speech, government, etc. This can be challenging, even for the writer who embraces world building. Luckily, you don't have to look far to locate advice on how to create your own world. Just this week, the Writers Digest website ran the following post:
If you've ever considered creating a world, the author of this Writers Digest article provides some great tips. And she should know something about it because...well, read the article, you'll discover why.