Think of History as where all work (or Activities) that has been closed or completed resides, along with e-mail correspondence. Similarly, when you send an e-mail from CRM or from Outlook and select the Track in CRM option, this is where you find the history of that e-mail.
As with the Activities section, you have the option to run manual Workflow via Run Workflow, located at the top of the screen. The History shows the last 30 days and filters on This Record Only.
For more information about using the History, see Chapter 9.