Small papers with a glow around them, looks like a musical note on the map.
They work pretty much the same as the almanac pages in AC3 in whereupon the player gets in range and position they start floating away and you have to quickly freerun through a number of obstacles and grab the paper before it floats straight upwards and disappears at which point you'll have to go away for a while and it'll return shortly so that you can try catching it again.
In this game it's partially for completing the collectible goals of areas and partially for giving the ship crew new songs to sing when you sail around on the sea map.
So can you add iguana or ocelot skins or whale via the editor now or not? You couldn't before, only the ship upgrades with the four main ingredients.
The user means that you can give yourself a massive amount of money using the editor and buy as many skins, bones, ETC from the general store.