Var is a programming keyword used in several languages, such as JavaScript and Python, to declare a variable. A variable is a storage location in a program that can hold data, which can be changed during the execution of the program. Using var allows developers to create variables without specifying their data type explicitly, making the code more flexible. In JavaScript, for example, using var creates a variable that is function-scoped, meaning it is accessible within the function it is declared in. However, it can lead to issues like variable hoisting, where the variable is accessible before its declaration. This behavior has led to the introduction of let and const in ES6 for better variable management.