.BO2 File Extension
What is a BO2 file?
Minecraft BO2 object file used by TerrainControl, a Minecraft modding application used to generate worlds; stores Minecraft terrain objects; also contains settings that control when sunlight, darkness, water, and lava are spawned in the world.
BO2 stands for Biome Object Builder version 2. The BO2 format was eventually replaced by the .BO3 format with the release of version 2.4 of Terrain Control.