Shirataki (shee-rah-TAH-kee) noodles are thin, low carb, chewy, and translucent traditional Japanese noodles. They are also sometimes called konnyaku noodles. Shirataki noodles are thinner than wheat noodles, do not break as easily, and have a different texture. They are mostly composed of a dietary fiber called glucomannan and contain very few calories and carbohydrates. They do not have much flavour by themselves, but absorb flavours well from other ingredients you can combine them with. Shirataki noodles are made from Konjac flour, which comes from the roots of the yam-like Konjac plant grown in South-East Asia.
If you buy them in their pure form, you can prepare them by boiling them briefly or running them under hot water, then combining them with other dishes, or adding things like tofu, garlic, spinach, or soy sauce to enhance the flavour.
Fun fact: The word "shirataki" means "white waterfall" in Japanese.