I have a link for you that discusses the Approval workflows in greater detail:
http://office.microsoft.com/en-us/office365-sharepoint-online-enterprise-help/all-about-approval-workflows-HA102280698.aspx#ReassignTask
As well as a link with information regarding three-state workflows:
http://office.microsoft.com/en-us/sharepoint-help/use-a-three-state-workflow-HA102771430.aspx?CTT=1
paulgilbride.com 