Instant messaging
Instant messaging is internet communication in which users exchange text messages in near real time, typically through an application or service.
Presence information: Status data indicating whether a user is available, busy, offline, or otherwise reachable. It lets messaging services show whether contacts may be ready to exchange messages.
Compatible Time-Sharing System: An early operating system developed at MIT that supported interactive computing and messaging between users. Its 1960s commands included early forms of direct user-to-user text communication.
WhatsApp: A messaging application that supports internet-based text, voice, video, and group communication. It exemplifies mobile messaging tied to phone numbers and end-to-end encryption.
Email: A system for sending and receiving digital messages through networked mail servers. Email is usually asynchronous and better suited to messages that need not prompt an immediate exchange.
Message queue: A system that stores messages until a receiving service or device can process them. Queues help deliver messages when a recipient is temporarily disconnected.
Talk (Unix utility): A Unix program that lets two users hold a real-time text conversation across networked computers. It brought terminal-based, live conversations to networked Unix users.
WeChat: A Chinese multipurpose application combining messaging with social, payment, and service features. Its ecosystem shows how messaging can become a gateway to many digital services.
Text messaging: The exchange of short written messages between mobile devices, commonly through cellular services or internet applications. The phrase overlaps with instant messaging but often emphasizes mobile phone-based texting.
Push notification: An alert sent by a service to a device or application, often while it is not active. Notifications bring incoming messages to users without requiring the app to remain open.
Internet Relay Chat: A protocol and network system for real-time group and private text conversations. IRC established enduring patterns for channels, nicknames, and direct messages.