Answer by
LeheckaG (1826)
"Sateen sheets" are made out of a tightly-woven cotton-fabric with a "satin-like feel and luster".
In general, higher thread-counts per inch result in a smoother feel.
Sateen-sheets do not "breathe" because of their tighter-weave,
so they are better in colder than warmer climates/weather.
Some people find sateen "too slippery".