In JavaScript, var is a keyword used to declare variables that are function-scoped or globally-scoped, optionally initializing each to a value. The syntax for declaring a variable using var is var variableName = valueOfVar; . The scope of a variable declared with var is one of the following curly-brace-enclosed syntaxes that most closely contains the var statement.

Some key points about var in JavaScript include:

• var variables are hoisted at the top and are initialized before the execution of code with a default value of undefined .
• Variables declared using var are function-scoped and cannot be accessed outside the function.
• var variables can be redeclared without triggering an error, and the variable will not lose its value, unless the declaration has an initializer.
• var variables can be used to declare global-scope variables.

It is important to note that var has some limitations and drawbacks, which led to the introduction of let and const in ES6.