Villager trading in Minecraft: professions, workstations, best trades
Villagers sell Mending books, enchanted diamond gear and Bottles o' Enchanting for emeralds.

The Emerald is the currency of villagers and the wandering trader: almost every trade is paid in emeralds, or earns you some. You get it from trading, from loot chests and from emerald ore, which only appears in mountain biomes.
It is made with the Crafting Table from Block of Emerald (other recipes also exist).
The usual way to get emeralds is to sell villagers what they ask for: crops to a farmer, paper to a librarian, sticks to a fletcher, coal to an armorer. With those emeralds you then buy enchanted books, diamond gear, food, maps or rare blocks. The wandering trader also sells plants, coral and other hard-to-find blocks for emeralds.
Emerald ore is rare and hides inside the stone of mountains; mining it gives one emerald, more with Fortune. Desert temples, jungle temples, buried treasure and archaeology sites also hold some.
Nine emeralds make a Block of Emerald, one of the blocks a Beacon pyramid accepts, and a single emerald pays for a beacon power. Emerald is also one of the armor trim colors.
Block of Emerald → 9 × Emerald
Emerald Ore → Emerald
Emerald Ore → Emerald
// Slots with several items cycle through every accepted option.
Villagers sell Mending books, enchanted diamond gear and Bottles o' Enchanting for emeralds.
A Cartographer villager sells an Empty Map for 7 Emeralds at the Novice level, and buys 24 Paper for 1 Emerald.
Librarian villagers sell an Enchanted Book for emeralds and a Book at levels 1 to 4.
At the Crafting Table: 1 × Block of Emerald gives 9 × Emerald. In a Furnace: 1 × Deepslate Emerald Ore gives 1 × Emerald. It can be found as loot in Trial Chambers, Buried Treasure, Shipwreck, Ocean Ruins and 6 more. It is dropped by Evoker and Vindicator.
It is the currency of villager and wandering trader trades, pays a beacon and colors armor trims. It is an ingredient in one recipe: Block of Emerald.