Gender means the state of being male or female. It is used in grammatically to ideentify a noun or pronoun weather it is male / female or none of this. If any noun /pronoun indicates neither male nor female ,then it may be common gender or neutral in gender.
Read the bellow sentences:-
Rahim is an old man.
Hehas three children.
His wife is a young lady.
She does everything in her house.
Here the words Rahim,He,man indicate being the state of male.Again wife,lady,she indicate being the state of female. Children indicates being the state of both male and female .But house everything can’t be identified in gender.