Final answer:
VoIP is the system that allows users to have voice communications over the internet.
Step-by-step explanation:
The system that allows users to have voice communications over the internet is called Voice over Internet Protocol (VoIP). VoIP is a technology that enables the transmission of voice signals over the internet, allowing users to make phone calls using an internet connection instead of traditional phone lines. It provides a cheaper, faster, and better-quality voice communication experience, and has given rise to spin-off technologies like free internet-based calling and video calling.