[Zope] Confusion about thread safety

[andre]

Hi,

after reading several things about thread safety, i'm a little bit 
confused by the fact that the words threads and connection are used in 
too various contexts.

So i'll ask a simple question.

With a basic Zope server, without any other DB, what happens when two 
different users want to commit changes made to the same object at the 
same time ?

are the two requests, two different threads ? ZODB speaking.