Tutorials/Void Trading

Void Trading is a trading method that allow players to trade infinitely by unloading a chunk where a villager you're trading with is located while the trading window is located, and then making the trade while the villager isn't rendered.

Purpose
Void Trading is used when you need a large amount of materials that can only be acquired consistently from a villager, like quartz, XP bottles, apples, golden carrots and redstone. The reason why they're called void trading is because the most common method of doing this trick is in the End, however, ianxofour has made a method without using the End.

Madman25
This is the origin of the name of Void Trading. It uses end gateways to teleport players thousands of blocks away, making it faster than ianxofour's design. However, it would require some bedrock removal and of course, killing the dragon itself.

Link: https://www.youtube.com/watch?v=82oPq0LkmYU and https://www.youtube.com/watch?v=5UfOzQZsoVo&t=0s

Ianxofour
Ianxofour made an even easier design than Madman and it doesn't require players to go to the end. It works by having a long railway, on one endpoint is a villager and in the railway is the player. By setting the render distance to 2, opening the trading UI and turning the railway on and letting you go to the other endpoint, you can do the trade and once you go back, the villager's trades aren't locked, allowing you to do this consistently. You can also have another villager waiting in the 2nd endpoint, making this more efficient.

Link: https://www.youtube.com/watch?v=FGFoCfRaljM&t=168s