Question : Asterisk PBX beginner

i read some articles and i get to know that software based pbx we can create unlimited extensions.
how does it works? does it create a virtual port for each extension or is it hardware based?
if i buy a 4 port interface card i can connect 4 phones?

Answer : Asterisk PBX beginner

If you use VoIP phones then they can connect over IP. The phones talk to the PBX and basically log in using a username and password. Asterisk can then dial any of the phones.

Interfaces are used to connect to analogue and digital traditional phones and telephone lines. So if you wanted to link your voip phones up to 4 analogue telephone lines you will need at least a 4 port analogue interface card.