Favorite and follow channels

Favorite a channel to keep it visible in your teams list or follow it to get notifications and stay up to date on new channel activity.

Favorite a channel

From within the channel, select Favorite next to the channel name.

Or, select more channels in the teams list and then select Favorite next to the channel.

Follow a channel

In the teams list, go to the channel name.
Select More options > Follow this channel.

Source: Microsoft