can someone explain me the difference between asterisk and zaptel ?
in all asterisk config i have there is lines containing zaptel.
Here you can find a lot of info on Asterisk voip-info.org/wiki-Asterisk
and in particular about zaptel here
Asterisk is a softswitch/PBX/ACD/and many other things, while Zaptel is an opensource set of drivers for TDM hardware cards. This is simplified, but gives you an idea.