Override Veto: This occurs when each chamber of Congress votes on a bill vetoed by the President. To pass the bill over his objection requires two-thirds vote in each Chamber.
Line-Item Veto: This is when an executive authority (like a governor or president) has power to nullify or cancel specific provisions of bills without vetoing entire legislative packages.
Executive Order: An order issued by leaders (like presidents) that manages operations within federal government. The legal or constitutional authority for executive orders resides in the vested executive power.