Udon are white and thick wheat noodles which are basically made by kneading wheat flour, salt, and water. Dried, pre-boiled, and fresh udon are available at stores. To cook udon noodles, following instructions in the packages is best since cooking time differs in each kind.
There are many udon dishes cooked in Japan. Udon can be served hot or cold. You might have seen udon noodles in hot soup (even a one-pot version) or fried udon noodles. Chilled udon noodles are also popular during the summer. They are eaten by dipping into noodle dipping sauce (mentsuyu) which is soy sauce flavored dashi soup. Bottled mentsuyu can be purchased at Asian grocery stores. Commonly, chilled udon noodles are served with various toppings, such as grated fresh ginger, nori (dried seaweed), chopped green onion, wasabi, sesame seeds, and so on. It's OK to make slurping sounds when eating udon noodles in Japan.