In Email - Campaigns; press the '+ Add' button to add a new email campaign. Campaigns are linked to websites so that the user can unsubscribe at the right website. The description for your campaign is for internal use only.
Users can unsubscribe from single campaigns. So organise and sort your emails in different campaigns to make the content relevant for your community.
If your not using a campaign anymore, you can easily hide it from the campaign overview.