I think the 09 and 10 have something to do with mac builds and windows builds, I'm not too sure. Just click one of the links and you'll either see something that says mac or win32 (or possibly something for linux) in the file name.
The difference between the trunk and branch (ones that don't say trunk) is in the Firefox Branch/Trunk Builds FAQ -
http://forums.mozillazine.org/viewto...8be85d905e79a3 Unfortunately, it doesn't explain much to me either. I think the branch ones have new features added and they have the possibility of more bugs.
If you want to see the fixes in each date's build and the new bugs (if any) go to
http://www.squarefree.com/burningedge/
EDIT: And the trunk and branch builds are both nightlies. If you want a stable release, you want the milestone. The current milestone release is 0.9.2 - it includes the fix for the latest vulnerability, other than that, same as 0.9.1