Overworld Coordinates
Where your portal is in the normal world.
Nether Coordinates
Where you should build in the Nether.
Exact Portal Linking
For perfectly synchronized portals, you can calculate using exact decimal coordinates rather than rounding. A single block in the Nether corresponds to exactly 8 blocks in the Overworld. Using decimals guarantees your portals never cross-link, which is crucial for complex Nether hub designs or when portals are built tightly together.