Who Is Hussain ?

Asalamualiekum !
Once a person was sharing seat in a bus with me, we shared lot of knowledge together. Later after all he told me to email an introductory note to his email about who was prophet's grandson Hussain. Who is so popular in shia dominated circles of Kashmir and all over the world.
I mailed him :

so here is your answer for Who was Prophet's grandson Hussain?

Imbibe in the name of Hussain
with his name comes the bliss
though his spring lost in deserts of Iraq
his treasury has yet vacant threshold
raise your hands and ask your wishes
in the name of his Baby Doll
in her name is Love for Dejected
generosity of Hussain extends beyond
even a handful of dust from his grave
beseech to it in the name of Infant Asghar
I love to call it Khaak e Shifa
heals the incurable wounds of heart.