VoIP Hardware/Software

For example from your regular phone with a peoplefone box
 

Or with an IP-phone directly connected to the internet

Or with a small digital communication hub

 

If your computer is connected to the internet, you can download a VoIP software named softphone and make calls with the help of a headset, a USB phone or directly with the microphone and loudspeaker of your computer.
 

You can download a softphone according the operating system on your computer: