Relative and absolute coordinates
When you provide x, y, z coordinates in commands. You can either provide relative coordinates or absolute coordinates.
Relative means coordinates start "immediately to the South East (SE) of where I am standing now"
Absolute means coordinates start "in the North West (NW) corner of the world"
- fill ~0 ~0 ~0 - Fill the block immediately to the South East (SE) of where I am standing now with dirt.
- fill 0 0 0 - Fill the block in the North West (NW) most corner of the world with dirt.
If you try the second command you may see nothing happen as that coordinate may be underground. Instead try filling the block higher up with a y-coordinate of 16. The y-axis in the world is the up direction.
- fill 0 16 0 - Fill the block in the North West most corner of the world and 16 blocks up with dirt.
Usually you will want to use fill with the ~ symbol for relative coordinates.
Use the . key (fullstop key) to show and hide your current coordinates in the world.
The ground plane of the world is a 64x64 grid of blocks.
As you move around the world on a flat area, your x and z coordinates will change.
As you move West or East, your x coordinate will change.
As you move up or down, your y coordinate will change.
As you move North or South, your z coordinate will change.
When you are in the North West corner your x and z coordinates will both be 0.
When you are in the South East corner your x and z coordinates will both be 63.