Teams are made up of channels, which are the conversations you have with your teammates. Each channel is dedicated to a specific topic, department, or project.
By default, all members of a team can create channels. A standard channel is open for all members and anything posted is searchable by others. If you need a smaller audience for a specific project, you can create a private channel for your team.
To create a private channel for a team:
Go to the team you want to create the private channel for and choose More options
> Add channel.
Enter a name and description for your channel.
Under Privacy, select the down arrow on the right, and then select Private – Accessible only to a specific group of people within the team.
Select Add. This adds a private channel to the team.