Tamarind is a huge tropical tree. Pulp from its husks has a specific sour taste and it is a base of well known worcester sauce. It is used for medical purposes too.
Pulp is used in many cuisines in Sout East Asia. If you get fresh husks, first remove the tiny shell by fingers and then separate the pulp from seeds, using your fingers again. You can mix it with a little bit of water too before adding to a dish.
Tamarind can last months without conservation.
Recipes with tamarind.