A Collection can be deleted in your workspace, with or without deleting the files inside. Either way, the Collection and the files inside are moved to the trash. Files and Collectons are held in your trash for a certain number of days depending on your Stockpress tier.
If you are an admin or your user role allows you to delete, you can restore files and Collections from your trash. If your user role has permission to permanently delete files, you can also empty the trash, which permanently removes the files from your workspace. This can NOT be undone!