When people say that the Japanese "take their shoes off" when they go inside, you're only hearing half the story. Many places in Japan have you take your shoes off, sure. But, you also often put on another set of shoes. Sometimes they are slippers, but other times they are special "inside shoes."
For places you frequent a lot, "inside shoes" (also known as "hallway slippers") are a very common thing. They are pretty much just softer, more comfortable shoes that you only wear inside when you are at a particular place, be it school, work, or various other public establishments. You might have a little cubby to keep your "inside shoes" in. A quick Google Image search will show you what they tend to look like.
In Japanese, these "inside shoes" have several names. @Nmurayukihiro on Twitter tried to figure out what these names were based on region in Japan. I had always known of these shoes by the name うわばき, and I was surprised to learn that they went by a few other names as well:
The most common, in order of popularity:
Red: うわばき (uwabaki)
Blue: うわぐつ (uwagutsu)
Yellow: ズック (zukku)
Green: バレーシューズ (bareeshuuzu / balet shoes)
Pink: Some instances of うちばき (uchibaki) and スリッパ (surippa / slipper).
It's interesting to see how one word can be so different depending on where you are in a country. I guess it's a lot like the words "soda" and "pop" in America.
Header image by Tatsuo Yamashita