These six forms refer to someone or something being spoken about. The same written form can serve both masculine and feminine dual: context tells you which meaning is intended.
Attached object
Meaning
Complete form
هُ
him (one male)
ضَرَبَهُ
هُمَا
them (two males)
ضَرَبَهُمَا
هُمْ
them (males)
ضَرَبَهُمْ
هَا
her (one female)
ضَرَبَهَا
هُمَا
them (two females)
ضَرَبَهُمَا
هُنَّ
them (females)
ضَرَبَهُنَّ