Minecraft wiki entry for Before_Village_%26_Pillage, associated text: Pressing use on an adult villager would open a GUI allowing a player to trade with the villager. Villagers would make offers based on their profession and career, and would only make trades based on what offers they were making. Different offers could be viewed by pressing the left and right buttons next to the currently displayed offer. All offers involved emerald as a currency, and some item pertinent to the villager's career.