Does anyone know what this Japanese symbol is?

Question:

It's usually on lanterns and red.

http://www.shutterstock.com/pic-13688041/stock-photo-row-of-traditional-japanese-lanterns-under-the-wooden-temple-roof.html

Answer:

It's called "Mitsudomoe"(= triple Tomoe) , and it's hard to explain what the symbol is.
According to wikipedia
-Mitsudomoe http://en.wikipedia.org/wiki/Mitsudomoe
-Tomoe http://en.wikipedia.org/wiki/Tomoe

There are two kinds of the symbol. Spinning clockwise and anti-clockwise. I don't know what is the differences, though.