This is the client’s gender, which is an attribute of the player’s key. By default, when a new mob is made for a player (in client.New()), the new mob gets the same name and gender as the player’s key. This influences text macros like he, which may expand to “it”, “he”, “she”, or “they”. Valid values are:

"neuter"
"male"
"female"
"plural"

See also