Living in Skyrim must be like having Charlie Kaufman as your god. You'd be pottering along, chopping wood, checking the sky for falling dragon poop, just doing your best as a person living in interesting times. You're not noticing the changes that are happening right under your nose: the flowers look prettier, you can't speak when you want to, and before you know what's going on there's an airship overhead. The hands of mod, reshaping your reality. I expect most of the inhabitants have just woken up to the new neighbouring landmass of Falskaar. The mod adds a remarkable amount of new stuff to base Skyrim, clicking in a new continent of content for you to play. Everyone seems to be talking about it, and with good reason.
Take a bow, Alexander J. Velicky. You certainly corralled a lot of stuff into Bethesda's wander 'em up. Expect to sink over 20 hours in if you want to see it all. 9 new story-quests and 17 new side-quests across a world that's roughly a third of the size of Skyrim. But it's the incidental touches that most impress: all of the dialogue has been recorded, with over 30 people adding to the accent of the world. From what I've heard, they're at least on par with the main game's vocals. 40 new minutes of music have been specially recorded just for the mod as well.
This doesn't have any effect on the rest of Skyrim, so you don't need to worry about the main game being taken over and filled with new spells or NPCs. Just treat it like DLC and leave it installed, to be visited when you feel like a nice new view.