I have view everything and still can' find one thing

There is nothing told me what is FreePBX… like you link me to your previous project and I look everyhing and I still don’t get it,…
What is FreePBX, what is it used for? I mean… I don’t see anything that show me(a end user) why I need that script for…
and it mentioned PBX… then what is PBX…
:?:
so can anyone tell me?

A GUI for Asterisk…

No wait a VERY NICE FUl Feature GUI for Asterisk…

Next Question I guess is what is Asterisk
Open Source telephony switching and private branch exchange (PBX) daemon