what in the name of all toasted frogs is a Pillow Book?

So I just realised that there are probably some people out there who doesn't know what a pillow book is. Since this is something I very often post maybe I should explain it.

The pillow book started with Sei Shonagon a court lady in Japan in the Heian era. She wrote about daily things that caught her eyes or ears, such as gossip, events or just things she noted or ranted about.
In short a pillow book is a literary work that is not a novel or poetry. A sort of diary.

I personally use it when I have something to say that doesnt fit the category of fanfiction, novellas or poetry.

It just so happens that there is a movie called "The Pillow Book" - its an amazing movie, very poetic and sensual.