Word, Excel, and PowerPoint are common to both of the Office 2007 editions you mention. The differences are Outlook, One Note, and licensing terms.
Office 2007 Home and Student Edition includes Word, Excel, PowerPoint, and One Note. A retail-box copy of Office 2007 Home and Student Edition is licensed for installation on a maximum of three computers in the same household for use by members of that household, subject to the limitation that the software cannot be used for any commercial, non-profit, or revenue-generating business activities. An OEM copy (which would usually come preinstalled by the computer manufacturer on a new computer) of Office 2007 Home and Student Edition is only licensed for installation on the computer that the software came with, and cannot be legally transferred to or installed on any other computer, and is also subject to the limitation that the software cannot be used for any commercial, non-profit, or revenue-generating business activities.