Work log can be an email or just a work log, and you can switch between these windows using the «Email» and «Work log» buttons:
When a work log or email is created in the case, it will also create a history log. User or other recipients will receive a regular email in their email client and reply to this as usual in their email client. Reply to an email will be entered to the correct case. The agent receives an email when there is a new email sent to his / her case.
From a log, you can create an FAQ with the icon 
Private log
Work log / email marked as Private is not visible to user on user web.
