[GIS] Convert an area to meters² in PostGIS

Question

I have this query :

SELECT ST_AREA(geom::geography) FROM region

The (geom) contains polygons from a shapefile imported into PostGIS with shp2pgsql.
I've appended ::geography, else the result of the function was displayed in degrees.
Now, I have this kind of answer :

544163926.22948

How can I know in which units it is displayed ? square/meters ? square/foot ?
I want it to be displayed in square/meters (m²) ou square/kilometers (km²)

How can I do that ?

Answer 1

The PostGIS Docs for ST_Area() say:

For "geography" area is in square meters.