Soba is a Japanese noodle made from buckwheat flour, often blended with some wheat flour since pure buckwheat dough is fragile and hard to shape. Buckwheat is a fruit seed, not a grain related to wheat, and it grows well in Japan's cooler mountain regions, including Nagano and Hokkaido.
Soba is served two main ways: zaru soba, chilled noodles dipped in a cold soy-based sauce, and kake soba, served hot in broth. It has a nutty, slightly earthy flavor and a light chew, typically topped with grated daikon, scallions, or nori, and it also appears fried alongside tempura.
Do not confuse soba with somen (thin wheat noodles) or udon (thick wheat noodles) - soba is defined specifically by its buckwheat content, and the ratio of buckwheat to wheat flour (often labeled on packaging, such as "juwari" for 100% buckwheat) affects how easily the noodles break when cooked.