This feature lets you close a channel instantly.
How it works:
In the sidebar, right-click on the channel that you want to close and you will see the close channel option. Click on it to close the channel.
Also if the channel remains inactive for more than 15 days then the channel is automatically closed.
Closing channels that no longer are active is great to reduce clutter in your workspace. You can open a channel to discuss something and once the discussion is over, you can close the channel.
Instead of texting multiple people, you can create a channel, discuss everything there, and close the channel once you're done. This not only saves you time but also is a quick and efficient way of conveying information to teammates.