[Asterisk-Users] Basic help

[asterisk]

I've read the FAQ and I've printed out the handbook and read it thru but I can't get hold of a basic concept.   How do I connect extensions to the system.   Eg I have 2 analogue telco line I gather I need 2 analgue board to handle them and bring calls into my system.   Question 1. Can I use normal analogue handsets if so do they also go into similar analogue boards ?   Question 2. Can I use sound cards & head sets in LAN connected PC?   Question 3. My only previous telephony experience has been with Dialogix boards. Can they be used with Asterisk ?   I know I should have been able to deduce the answers from the documentation but I couldn't. Any help gratefully received.