Japanese food is quite varied. Some of the more common Japanese dishes include... noodle dishes (such as ramen), rice bowls (donburi), and sushi. Japanese dishes are generally very healthy, often include some sort of sea food, and typically contain white sticky rice and vegetables.
Ramen is one of the most common noodle dishes within Japanese food. There are many different flavors and ingredients (and, no, this is nothing like instant ramen) but the most common type of ramen is made with a soy sauce (醤油 - shouyu) broth. A big bowl of shouyu ramen often also includes a great deal of ramen noodles, bean sprouts (もやし - moyashi), dried seaweed (海苔 - nori), pickled bamboo (支那竹 - shinachiku), and green onions (長葱 - naganegi). A slab of cured pork called chashu (チャーシュー) is also a favorite "topping".
Other very common types of noodle dishes can be made with udon (饂飩) noodles (which are very thick noodles) or soumen (素麺) noodles (which are very thin noodles).
Donburi are another very common type of food in Japan. The most common being katsudon (カツ丼) - a rice bowl made with eggs, sautéed onions, and breaded pork (カツ - katsu); oyakodon (親子丼) - a rice bowl made with eggs, sautéed onions, and chicken (it means "parent and child bowl"); and gyuudon (牛丼) - a rice bowl made with sautéed onions and beef. There are many different types of donburi but the one commonality amongst them is that the toppings are always placed on a bowl of white sticky rice.
White sticky rice is a staple of pretty much every Japanese meal. So much so that the word for cooked rice (gohan) also means "meal". The stickiness makes it possible to eat with chopsticks (箸 - hashi) which are the primary utensils in Japan. Be sure to always lay your chopsticks across the top of your bowl or on the table and never leave them sticking out of your food - this is only done at funerals and is considered very bad luck.
Wasabi is a green Japanese horseradish sauce. It is very strong and should be used in moderation. A small amount is typically placed underneath a piece of raw fish on a piece of Nigirizushi. This is both for taste and also to help kill bacteria.
"Daikon" literally means "big root". It is a Japanese radish that is often grated into the soy sauce meant for dipping sushi into to help kill any bacteria that might be in the sashimi (raw fish).
Soy sauce is very common in Japanese cooking. It is also often used for dipping, especially certain types of sushi (Nigirizushi and Makizushi). Soy sauce is made from fermented soy beans, water, and salt.