asterisk users - Oct 2003 - Communication between 2 telephones

Hi!

I have installed everything, asterisk, pwlib,openh323, chan_oh323. And now?
I want to install ophone to talk, but I don't see what is the asterisk role.
I mean, ophone lets us to talk with another phone,... why do we need
asterisk? What does ophone do and what dows asterisk do?

Thanks for all your help

Mireia