The term "border wall" refers to a physical barrier or structure that is built along an international border between two countries in order to control and regulate the movement of people, goods, and resources across that boundary. The purpose of such walls can vary depending on the specific context but generally they are intended to prevent unauthorized entry, reduce crime and terrorism, and protect national security. In recent years, the term "border wall" has become a politically charged phrase in the United States due to debates over immigration policy and border control.