Minecraft is a game where the player creates and destroys worlds, objects etc. using blocks, the game at this moment in time is still in beta mode and has been in development since 2009. It is possible to make changes to maps by moving blocks from one map to another, one such program for this is MCEdit, the files that are created when a world is edited use the .schematic file extension.
» MCEdit Level Editor
How to open .schematic files?
Software to open .schematic files
What are .schematic files