Page cache and fragment caching

Hi,

I'm looking for a good explanation on how to do fragment caching in Drupal. From what I understand, the "page cache" caches ALL the page, including the blocks, and not simply the "$content" variable found in page.tpl.php. Is there any documentation anywhere explaining :
- The different caches
- When they expire
- Which part of the page exactly they cover

I come from the eZ Publish world where you can basically define rules for pretty much any part of any page regarding caching and expires of caches.

I want to optimize a page so that every single part is kept as long as possible, ie: each block should only expire when it has to (when the content it displays needs updating). For a weather block, that might need to update every 10 min on all pages. For a block of last X articles, it would be when a new article is created (but not when a page is). I haven't been able to find proper documentation that would tell me for sure if :
- the weather block would show the version cached when the page was last updated
- each update of a content clears the cache for every other page in the site
- etc.

My next step is probably doing step by step debugging to figure those rules out, but I'm baffled to not have found them explained clearly anywhere so far.

Any link ?