Henna has traditionally been used to decorate the hands and feet during weddings, festivals and other special occasions. The powder (made from the henna plant) is mixed with water to produce a paste. Usually the henna is painted directly on to the hand or foot in intricate patterns. In these modern times, there are also ready made stencils to use that are imported from the Middle East.
When you visit Morocco, it will be easy to find a henna artist to decorate your hands or feet if you'd like to try it. The pattern will usually stay on your skin for 1-2 weeks before fading.