Slack is a channel-based messaging platform. With Slack, people can work together more effectively, exchange information or documents without using emails.
In Slack, team members send messages and share files in channels. You can create channels for team work, projects, subjects, or anything else that’s relevant to your organisation. You can make channels private for conversations that shouldn’t be open to all members, or you can use shared channels to collaborate with external organisations from your own “workspace”. You can start a voice or video call with any other members of your workspace right from Slack. Share your screen to show your teammates exactly what you see on your computer, you can even draw on your screen while you’re screen sharing. Slack has a free version with some limitations. In particular, with the free plan old messages are automatically deleted.