Unlike movies, we don't have CGI-created visuals to accompany us when we're reading a book. We have to rely on our good, old noggins to supply us with images. Especially when we're reading Sci-fi/Fantasy, or anything that falls under the Speculative Fiction genre.
The thing with worldbuilding is that it's all too easy to fall into the old info-dumping technique. You're the Creator of your world, and of course you want to acquaint the reader with its grandeur so at the very first instance, you bombard us with several long paragraphs detailing every hill, castle, and hybrid creatures existing in your creation.
Um, not good. You'll run the risk of putting your readers in snooze town.
Or you can go the other way: You skimp on the worldbuilding descriptions to allow for a fast pace read.
Erm, not good either. If we find ourselves scratching our heads, then it means you've lost us. How the heck are we supposed to know what a kipa is, and why does your character keep saying "sika!"? (Those are actual words found in my MG Fantasy WIP. :D )
There has to be balance. The aspects of your world should be interwoven within the scenes and around your characters' actions. A sentence here or there explaining certain things will not bore your reader (as opposed to huge blocks of descriptive text).
Here's an excerpt from my MG Fantasy WIP: