Shao-e-henna usually occurs the night before the wedding day, but sometimes families put a day in between so they get some rest before the wedding.
They do the henna, because that shows they are good people and honoring their parents. Normally, an unmarried woman will not henna her feet. Then at the henna party (and thereafter), she can put henna on her feet. She will also get henna on both of her hands (which unmarried girls do also).
The groom will get henna on just his right palm and the pinky finger only. This shows he is an honorable and good man. It's not in the Qoran, but is just a custom in Afghanistan.
The party will not often occur in a hotel, but usually in the home. If the family is wealthy and does not want to mess up their home, they will have it in a hotel. If in a home, they have separate parties for the girl and the boy. The girl's is at her home, and the boy's at his.
If they don't live far away from each other, then after the meals, say around 11pm, the boy along with some female relatives and sometimes female friends of the family will go to the girl's house.(Also, the boy must be free to go by his family' permission. If he is not free, then just his female relatives will go to the girl's house.
So when the boy or his family put henna on the girls hand, there are bowls up front that have sweets in them like chocolate, and Nuql and also bowl with henna. First the boy (or his female relatives) puts henna on the girl's right hand.
Time for tea - I'll finish tomorrow what happens when the boy arrives at the girl's house.
Return from Shao-e-henna to Afghan weddings