The email editor can be used to format your emails in a special way, to make your message more unique. The editor is available to create uniform and professional looking templates (done by Account Admins) as well as to send a customized email message.
How does it work?
Start by composing an email on an up sheet.
OR add a Template to the account if you would like to send a particular message on a regular basis.
For more details on this feature you can feel free to visit the CKEditor's User Guide which expands upon some of the capabilities.