The Landing Vehicle, Tracked (Lvt) is an amphibious warfare vehicle and amphibious landing craft, introduced by the United States Navy. The United States Marine Corps, United States Army, and Canadian and British armies used several LVT models during World War II.
Originally intended solely as cargo carriers for ship to shore operations, they evolved into assault troop and fire support vehicles. The types were known as amphtrack, « Amtrak », « amtrac », etc. (portmanteaus of « tracteur amphibie »), and « alligator » Ou « gator ».
Source: Landing Vehicle Tracked on Wikipedia