Summarize Tor Messenger protocols

Here is start why we should do this:

<@arma> sukhe: is there a simple summary of the xmpp protocol somewhere, from the point of view of metadata?
<@arma> like, do my messages go through the center server too? and if i'm on one jabber server and the other person is on another, do the messages go through both of them? or is it only presence?
<@arma> sukhe: also, if i am talking to two people, using xmpp, does my tor messenger have one tcp connection, over tor, to the central server, and it carries both conversations?