One of the new features in Outlook 2010 are tools on the Ribbon that appear on demand, as you work. These tools will automatically appear as you work with your messages. They will be relevant to what you are doing at the time.
For example, if you are inserting a table in an email, when working in the table, you will notice that the Ribbon in the message displays the Design and Layout tabs, along with Table Tools.
When you click out of the table, these tools are no longer displayed.