Kaffir limes are not true limes. They are from the subspecies of the citrus family and also known as makrut. In South-east Asia, the tree is found easily as they are the native to that part of the world. The rind of the dark green knobbly fruit is sometimes used in Thai cooking while the leaves are the most used. The flesh of the kaffir lime fruit is not edible.
Whenever the leaves are torn or shredded, they release out an unmistakable citrus smell. In Thai cooking, the kaffir lime leaves are used very extensively and also a popular flavoring in Indonesia, Malaysia, Burma and Vietnam cuisines. The leaves are either shredded finely or torn to be used in soups especially the hot and sour soups, and curries.
** Asian Recipes