Indonesians are taught since a young age to respect their elders. One manifestation of this is the way we greet our elders. We do not shake an elder’s hand, but we put their hand to our forehead. There are variations to this, such as putting the hand on your cheek or take an elders hand and “kiss” the hand.
Of course, you do not have to do this to all elders, only to those in the family and friends of your parents. And as you grow up…..it’s ok to drop this habit :)