Fortnite is a weird as hell project that is now dominating the world with 125 million users. What started off as a fully PVE (a mode called Save the World) joint that sought to capitalize on the survival genre is now a fully-fledged battle royale, and along with PUBG, is responsible for popularizing the subgenre that’s been around long before them.
In that sense, it’s two separate games. The PVE portion is still in early access and has loot boxes. Battle royale has a sleek season pass, offers zero items that impact gameplay, and is completely free.
I think you can guess which one I prefer.
Source: Destructoid Review: Fortnite (Switch)