Curry leaves are leaves of the curry tree, which is native to India and Sri Lanka. The leaves are dark green in color, shiny, and aromatic, releasing a unique, nutty aroma when fried in oil. They are a staple of South Indian cuisine, used in the same way as bay leaves are used in Western cuisines.
The leaves soften significantly when cooked and are usually used as a flavoring to rice, chutneys, dals, soups, and stews. They are such a staple of Indian cuisine that the Tamil word for them is karibeppilai, which is literally translated to the leaf that is used to make curry.