How does the relationship bugtracker'a and VCS?

Good night everybody, my question is:

I once worked on a project where I used a bunch of Trac + Subversion. Actually important, not these softiny, but in General the principle of action.

It looks as follows: in every commit I must specify the ticket number in the Truck, and then when you view the ticket can see the list of all commits to it.


And I'm still very curious how this works, because as I understand it Subversion uses a database, and Vice versa Trac pulls all the information from there (sorry never installed neither).


Thanks in advance to all who answer

Dmitry