The curry tree, Murraya koenigii or Bergera koenigii, is a tropical and sub-tropical tree in the family Rutaceae, native to Asia. The plant is also sometimes called sweet neem, though M. koenigii is in a different family to neem, Azadirachta indica, which is in the related family Meliaceae.
Curry leaves are generally used at the beginning of the cooking process or as a final flourish. Typically, they are combined with mustard seeds and coconut oil to form a bouquet of flavors. Pop a teaspoonful of mustard seeds in hot, shimmering coconut oil.