What is Pandan leaves ?

Pandan leaves
(Screwpine leaves, Pandanus latifolius, P. amaryllifolius)

Pandan is usually added to desserts or Herbal tea to add this really nice aroma.
It's kinda like when you add Vanilla to get the Vanilla ice cream smell.
(I always associate Vanilla smell with milk ice cream :P)
but Pandan leaves have a different milder kinda smell.

You bruise the leaves a bit or just simply tie a few leaves into a knot and boil them with your tea or add them before you cook your dessert.

More info here
http://www.asiafood.org/glossary_2.cfm?wordid=3294

Pandan also have some health properties
"The medicinal uses for this tree are as follows: The entire plant is used as a diuretic, the roots have anti-diabetic properties, and the leaves are used for treating diseases of the skin. "
http://www.essortment.com/all/pandanleaf_pga.htm