Voice over Internet Protocol (VoIP) is a different method of making and receiving voice calls. Rather than using a dedicated phone line to make a call, your phone service goes through your broadband internet connection.
You speak into your receiver.
Your voice converts into a digital signal.
That signal travels through your broadband service.
Once the signal arrives at its destination, it converts back into an analog sound.
Other than the delivery method, there are no differences between a VoIP calls and a traditional phone call.