Soba is a Japanese noodle which can be enjoyed in hot broth, cold broth or in a noodle salad.  It comes in original and 5 other variations - with quinoa, jinenjo (wild yam), yomogi (mugwort leaf), lotus root or cha (green tea) added.

About the additional ingredient in each variation
Quinoa - has the highest amount of protein among all grains and is exceptionally high in vitamin B and calcium.  It is a rich source of vitamin E and contains the amino acid lysine.
Mugwort - Mugwort leaf is a mild herb and gives the soba its deep green color and delicious flavor.
Lotus root - makes the soba a warming food.