There are two kinds of toilets in Japan: Japanese toilets and Western toilets. Neither of these are really like anything you are used to.
Japanese toilets are also referred to as squat toilets. They are called squat toilets because that is how you use them. Imagine a tall urinal installed in floor instead of in the wall. You have to balance yourself over the toilet, squat, and do your business. Many Japanese consider this to be cleaner, as you never touch that actual toilet. Given the precarious act of balancing over a toilet while you relieve yourself I never quite agreed with them. If it were not for the pipe at the head of the toilet that I clung onto for dear life I would have fallen in many times.
Western toilets are what we Americans are generally accustomed to. You sit down, do your business, and proceed on your day without any bathroom trauma. Generally. Except that some Western toilets in Japan come with remote controls and buttons. I will not begin to debate why I think toilets should not have buttons, let alone remote controls. Rather, I will explain what they do because pushing buttons on a toilet when you don’t know what they do can have some negative results. There are usually three functions with levels of intensity and placement.
The first is a seat warmer, to keep your bum nice and toasty on cold winter nights. This may be a nob rather than a button on some models. This funciton is rather pleasant as I’ve noticed many bathrooms in Japan, both public and private, are not always well heated (if at all.)
The second comes in different forms, but all has the same function. The idea is a white noise generator. The button will run some water, or play the sound of running water, or play music or a gentle humming sound. All there to disguise what you are doing on there (as if it’s some big secret.)
The third –and most important- button is the bidet, or washer. Sometimes the same button and sometimes separate buttons, the idea is the same. Water will be sprayed at your ass. By looking at the button you wouldn’t immediately know its purpose.
I cannot tell you how many people, including myself, have pressed this button out of curiosity and met with a big surprise. Precisely for this reason I warn you. I had more than one friend / coworker exit a bathroom with a look of horror and mutter something akin to “I think the toilet just raped me.”
Some toilets also come with blower functions to dry you off from the bidet.
One final note, bathroom but not toilet related. When you go to wash your hands afterwards (which for sanitations sake I hope you do) you will be hard pressed to find paper towels. In any public bathroom. Ever. Outside of major cities such as Osaka or Hiroshima you’re unlikely to find electronic hand driers either. Sometimes even in them. This is because most Japanese carry a handkerchief with them at all times to dry their hand with or wipe their brow when sweaty. It’s best you get one too. That is, unless you enjoy moist hands.