I need to learn what?

I think it is quite common in Taiwan. I remember seeing such signs in the Taipei Airport (they made an impression as at the time I wondered why this term was used).

Pretty common in the mainland too. It's often printed on signs. When we say it, we tend to use 洗手间 more often.

And I am certain that it is listed in one of the posts on the "same thing, different names" thread. Time to do some revision jbradfor.

It's only just occurred to me, but if you replaced the 'what' in the name of your blog with 'Chinese', you could save yourself a lot of bother.