I think a little comparison is in order ...

            What does each method need?
Method     telephone  PC   DSL/Cable/FiOS
======     =========  ==   ==============

LandLine   Yes        No   No

Vonage     Yes        No   Yes

Skype      No         Yes  Yes

MagicJack  Yes        Yes  Yes

I hope you can read my comparison table ... e.g. with a 'LandLine', you
need a telephone.; with 'Vonage', you need a telephone and a fast internet
connection ...

OK? 

HTH

--
Martin