Lifecycles control who can do what to an object at any state of its existence. The Lifecycles list in Web Apps Lifecycles describes the states for each lifecycle.
About Lifecycles Lifecycle Page Tasks/Signatures Page Tab Approvals Page Tab Adding an Approval Task Adding Approvers from a Route Template to a Task Approve Assigned Tasks Page Approving a Task with Signature Requirement Promoting an Item Promoting and Demoting Groups of Objects Running a Promote Trigger Validation Report