As the title shows, What are the differences between "CenterOfMass" and "Coordinates" in the PartType0 (gas) ?
The Coordinates is the Voronoi cell center, as in the description of CenterOfMass: "the center of mass, which in general differs from the geometrical center of the Voronoi cell".
The "Voronoi center" or "geometrical center of the Voronoi cell" both refer to the "seeds, sites, or generators" in the language of the wikipedia page.
We typically use Coordinates for all analysis, although the CenterOfMass gives a more accurate gravitational force calculation. The difference between the two for any post-processing analyses should be negligible.
Thank you Dylan, I got it.