Slack is a business messaging and collaboration platform built around persistent channels, direct messages, huddles (audio/video), and Canvas documents, with a large third-party app ecosystem via the Slack Platform API. Acquired by Salesforce in 2021 for $27.7 billion, Slack is generally credited with popularizing the modern team-chat category that Microsoft Teams and Google Chat later followed. It competes primarily on developer-friendliness, UX, and its App Directory ecosystem rather than on native voice/video breadth.