Known anatomically as nasojugal folds, grooves or lines.
This is where the eye socket meets the slope of the nose (the infaorbital area), which sometimes creates a prominent groove on the skin between this area.
Tear troughs may be more or less pronounced due to several factors. This includes body fat, skin density, health, and genetics. With those factors in mind, tear troughs are more prominent on average amongst women, Caucasians, older individuals, and those who are skinny or emaciated.
Some characters have pronounced tear troughs as part of their canon design, such as Sakata Kintoki from Fate/Grand Order.