IP Phone for Universal

[ynagy]

I know it could be a ;) silly question for some of you but I don't know how to operate and run IP phone to use it on my universal device
- Where I should download the agent?
- Is that something like soft-phone?
- Is that required to register with my phone company if not which provider?
- How is the quality?
- Is it secure and encrypted?
- Is my data plan on the phone will support it? Or do I need a WiFi?
Any information on this subject will be really appreciated.

Thanks,