If you have a German nationality you can be identified by your German social security number, in the same way, a computer with an internet connection can be identified by its IP address.
Recently I needed to voice chat with one of my friends today on Skype but didn’t want to download the desktop client.
There are some situations where you don’t want to install the desktop client and I fell in one of them.
All that’s is required to make free calls to people in United States, China or anywhere else in the world, is that they have installed Skype on their computer.
It’s also possible to make low-cost calling to people that don’t use the Skype service.
Since there are a lot of them I have listed them here separately from the other icons.