Final answer:
Instant messaging is the communication tool that allows multiple users to communicate with each other in real-time by using a smartphone application or social media site.
Step-by-step explanation:
Instant messaging is the communication tool that allows multiple users to communicate with each other in real-time by using a smartphone application or social media site. Instant messaging apps provide a platform for users to send and receive text messages, voice messages, images, videos, and more, allowing for quick and convenient communication.