Your team can talk about a variety of topics in Slack: projects, deals, deliveries, financials, cat GIFs, and more.
Most of this information is useful to everyone, but not every discussion needs to be seen by your entire team. That's why Slack provides a few different ways to have a conversation: channels, private channels, and direct messages.
When to use a channel or direct message
Channels are for conversations that are open to all team members. Messages posted to channels are archived and searchable to the entire team.
Private channels are best used for topics that are sensitive or confidential, or limited to a small group of team members. A private channel and its contents are visible and searchable only to the channel members.
Direct messages and group messages (DMs and group DMs) are useful for quick, private conversations between two or more team members. These conversations are visible and searchable only to you and the team members you DM.
Who can join a channel
Channels can be joined freely by any member of your Slack team. See Browse and join channels for more on discovering new channels on your team.