(Jingle support in asterisk is experimental)
Jingle is an xmpp based protocol for signalling the transfer of media.
Currently asterisk supports the proprietary GoogleTalk protocol that is
very similar to jingle, and hopes to soon support true jingle specs
(JEP-166,167,176,177,180,181 etc) as more clients support the true standard.
Jingle's configuration is very similar to sip.conf only as we are not the
jabber server in this case you must provide a connection for the peer to
travel out on.
chan_gtalk is for supporting the non-jingle google/libjingle spec and 
chan_jingle will continue to move in the direction of the correct spec.