Normally only the chunks immediately surrounding a player are loaded into memory. As the player moves through the game world, new chunks that come into range are loaded into memory and older chunks that are out of range are unloaded and saved to the disk. When a chunk is unloaded, all processing in that chunk stops. This means, for instance, that redstone machines and iron golem farms will only work if a player is nearby. This can make effective farming difficult when the player spends a lot of time exploring or in another dimension. Since spawn chunks do not get unloaded, they continue to process events, even when no players are nearby. Be careful when resetting the worldspawn (with the command /setworldspawn ). Setting it to a place that receives intense lag (for example, the Far Lands, or an area with a large number of redstone clocks) will cause that lag to be present no matter where you are