Call-through telecom providers use Voice over IP (VoIP) call termination to connect the caller to the recipient. Most of the call is carried over IP network, where cost of carrying of the audio signal is cheaper than traditional phone carriers. The calls that are initiated on the Internet (e.g. Skype) use VoIP. These calls can terminate at other point on Internet or even at the point, which is not on the Internet, e.g. traditional telephone line - this is known as call termination. The calls do not have to originate on Internet in order to use VoIP. A caller can dial a physical phone number, which is then routed over VoIP to the point when it is terminated at the recipient's physical phone line (fixed landline or wireless mobile or cell line), even in another country. This is what call-through telecom operators do - they provide call termination at both ends of the call.
United Kingdom of Great Britain