Install an IP PBX that can accessed by multiple people around the world

Hello All, this is probably an easy question for all of you.
I want an ip pbx that i can use an ip phone or adapter such as Linksys PAP2T so i and the rest of my friends can connect to it from anywhere in the world. I have access to leased line and public IPs or maybe host it in datacenter. I don’t really understand the technology or the terminology behind IP/voip/SIP PBX.
later on I want to connect a couple of land-lines to the PBX so i can use them when i connect with my ip phone/adapter.
can someone give me the basic idea with the right terminology … I’m ok with the rest of the IT technology but i need a push into the IP telephony.

thanks in Advance

Is google broken or down? :wink:

You might start here

This is a must read. Older versions are available online for free. I think the newest is the 3rd edition.

Asterisk: The Future of Telephony