The Landing Vehicle Tracked (LVT) was a class of amphibious

Amphibious warfare

Amphibious warfare is the use of naval firepower, logistics and strategy to project military power ashore. In previous eras it stood as the primary method of delivering troops to non-contiguous enemy-held terrain...

 vehicles introduced by the United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

, Marine Corps

United States Marine Corps

The United States Marine Corps is a branch of the United States Armed Forces responsible for providing power projection from the sea, using the mobility of the United States Navy to deliver combined-arms task forces rapidly. It is one of seven uniformed services of the United States...

 and Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Originally intended solely as cargo carriers for ship to shore operations, they rapidly evolved into assault troop and fire support vehicles as well. The types were all widely known as amphtrack, amtrak, amtrac etc., a portmanteau of amphibious tractor.
The LVT had its origins in a civilian rescue vehicle called the Alligator.