The plugin installs rclone. rclone is a command line program to sync files and directories to and from services such as:

• Amazon Drive
• Amazon S3
• Backblaze B2
• Box
• Dropbox
• FTP
• Google Cloud Storage
• Google Drive
• HTTP
• Microsoft Azure Blob Storage
• Microsoft OneDrive
• Nextcloud
• ownCloud
• SFTP
• WebDAV
• The local filesystem
• And many more

Go to http://rclone.org/ for more information.