Spawn

Spawning refers to players and mobs (creatures) being created and placed in the game world.

=Player=

When a world is created, so is the player spawn point. Your first view of your map is from this spawn point. The location of the spawn point can be changed if the player digs 3 spaces downwards from it. This will however only move the spawn point a few blocks away from the original location, it will not move the spawn point any great distance.

If you die in the game, you will respawn here. Most Tutorials advise marking this point, building a safehouse nearby, or otherwise making it defensible. Items that were in your inventory will be dropped at the place of death. Like all dropped items, they will disappear in 15 minutes if not collected.

In Multiplayer, the spawn point is set by administrators and can even be a Spawn jail.

=Mobs= Mobs spawn no closer than 24m, in a 144x144 area around the player's location after a short delay. A player running through the game world will usually keep ahead of the waves of mobs spawning at their previous locations. Mobs that get too far from the player will be removed.

Mob Spawning Science by fr0stbyte124.

Friendly mobs spawn in lit, grassy areas. Torchlight counts.

Hostile mobs spawn in unlit areas on any flat block. They will not spawn on Half Steps. There is also a special Mob spawner in dungeons.