The World, a cube, many blocks are generated in this blocky world. The generation of the world is made randomly each time a world is created, this makes each world unique, this makes every cave, every lava lake, every stone blob, every block part of a world that cannot be re-created. What happens to this world? It does what it was designed to do, to allow players to edit it, to take blocks from it, to gather resources so they may gain money which in turn they put towards the team bank so their team may beat the other team, or allow them to create what their hearts desire such as bases, statues, traps etc.
On multiplayer servers it does not happen in quite the same way, on public servers up to 10 to 50 unique players, some with no identity, blast away at the rock, during wars and base building but mainly during wars. Whenever some-one does what the world was created for, to build what their heart desires, or to gather resources to help their team beat the opposing team. A player goes and destroys the base, a player goes and starts a war, a player goes and destroys the players that try to play the game it was meant to be played because they can't think to do anything else. This only what happens part of the time, other times when the server is at peace, when co-operation is at it's greatest the very world yields it's gratitude that it may finally be used for what it was created for...
The computer generates a world using a series of calculations such as how many lava blocks there are, how much metal there is to be and so forth. The world generation may be configured in some ways by changing the config files of the server/client server.
The things that are created detirmine what the world is, if the world has a lot of surface lava then it may be called a Lava World, if it has a low amount of Metal/Ore but plently of Dirt , then it might be called a Dusty World etc. The things generated are not just the blocks you see althought they may make up most of it. Blocks are created first such as metal and dirt, stone 'Blobs' are added, then ores like gold and diamond are generated, then caves are generated, after which lava source blocks are created and the game calculates where the lava will flow at which point the generation is complete.
The order of this is based on a educated guess, the metal and dirt would make sense to come first as they are the base building blocks of the world, then the ores like gold and diamond come next because they are the goal of the game but are meant to be quite rare so placing them far enough apart from eachother is essential, next are the caves, have you noticed on the surface that there are pillar like formations that go up to the world height? it is my guess that the game generates the world with metal and dirt by filling the entire space granted with it then when the caves are added they go through the world but are more concentrated on the surface thus the real 'Surface' is on the pillar like formations. Next are the stone 'Blobs', they are generated after caves because I have yet to see a cave that cut through stone. Then lava is added, the lava is created in the caves so that the player will not be able to find easy exposed ores, also they are a hazard when attempting to break into caves.
In short the world generates in this order:
For the most part the world is pretty docile, Lava being the only thing that can kill a player besides a big fall, when a player edits the world, they cannot undo that edit, once they mine a block, that block cannot come back, if a world was to be completly eaten away at by players, there would be no way to reverse the effect as players can't under any circumstance place blocks generated by the world, the world would be converted either to a void that it is surrounded by or to a world created entirely by a player or many players.
The world is created in a area, it has a height just under the cloud level, with a base about half the world height above the floor of the universe, a floor where everything ceases to exist, the world is surrounded by a black area known as the 'Void', it is assumed that the world is created in this void alone, there is the possibilty that many other worlds are just out of sight, on the edge of the known universe where the clouds disapear, where the line between what you can see and what you can't is drawn, there may be other worlds out there, we will never know.
Infiniminer allows players to configure World Generation inside the Server.Config.txt file. The customizeable parameters inside the file include "includelava", and "orefactor". The orefactor field specifies the amount of Ore that will generate in a vein. The includelava field is pretty self explanatory (allows Lava to spawn in the world).