A virtual phone number is a number you can use anywhere in the world. You can also use it on any smart device in a flexible and seamless way to receive and/or make calls from/to your customers, regardless of their location. It uses the same technology as Google Voice, WhatsApp, and others. You don't need a SIM card, as you do for a cell phone number, because it uses secure internet technology (VoIP) for real-time voice communication.