How to build an XP farm from a spawner in Minecraft
Dungeons are small Cobblestone and Mossy Cobblestone rooms underground with a Monster Spawner in the middle.

A Monster Spawner is a cage that keeps creating one kind of mob while a player is nearby.
It is mined with a pickaxe.
Spawners stand in dungeons, mineshafts, Nether fortresses and strongholds. It works when you are within about sixteen blocks and the light allows that mob. It drops only experience, even with Silk Touch, and torches around it or breaking it stop the flow; built around, it becomes a mob farm.
This item has no crafting recipe.
Dungeons are small Cobblestone and Mossy Cobblestone rooms underground with a Monster Spawner in the middle.
The portal room has 12 End Portal Frames over a lava pool and a staircase with a silverfish Monster Spawner.
It spawns mobs and is the core of many farms.
The fastest tool is the pickaxe.
Placed under a Note Block, Monster Spawner gives the Bass drum sound.
No: pistons cannot move it.