The local variable carName cannot be accessed from code outside the function:

A GLOBAL variable can be accessed from any script or function.

If you assign a value to a variable that has not been declared, it will automatically become a GLOBAL variable:

Parameter passing is by value for primitive types (number, string, boolean).

Global names are obscured by the same local names inside functions.

Parameter passing for non primitive types is by reference!

Local names are obscured by the same local names inside called functions.