[TYPO3-english] What does cache_pagesection do?

[Urs Braem]

Hi! 

I've been pondering typoscript rendering (speed) questions lately. 
But I don't get ahead without basic understanding of how this works, and I can't find a comprehensive explanation online.

Could someone explain (or point to an explaining link) what information is stored in the tables cache_pagesection / cf_cache_pagesection?
The 4.5 install tool says "TS template related information". But what and how?

Thanks!
Urs