Just like any phone service, Spikko uses your mobile network or land line.
Spikko has agreements with local phone companies worldwide to provide the routing service to your phone. In addition, Spikko provides you with a local phone number for dialing out and receiving calls on.
You do not need a data plan to use Spikko (aside from initial installation).
Wherever you are, dial as normal; Spikko takes care of the rest.