*Xmas Update* you can now download the holiday llama at https://www.myminifactory.com/object/3d-print-holiday-llama-fortnite-80437
Llamas are the "lootboxes" in Fortnite, specifically available through PvE gameplay and not Fortnite: Battle Royale.
Also Real Life Fortnite Loot Llamas Found in London, Warsaw, Cologne and Barcelona as a promo for Season 5.
Llamas are ridiculously rare in Battle Royale, but often have many resources and items in it. It contains a varied assortment, from resources to traps to ammo. Unfortunately, there are no weapons. They seem to spawn in uncommon places like hills and roads, and not in named areas. The resources will contain 200 of each. They are the classic purple llama.