It means that
the Function constructor always creates functions in the global scope, while a function expression inside another function creates a function in that other function's inner scope; they're logically equivalent because
alert is a global function and
this is determined by execution context, not scope.
If the second example had created a variable named "alert" inside the outer function then the "alert" inside that Function constructor would still refer to the global alert.
If the first example had created a variable named "alert" inside the outer function then the "alert" inside that inner function expression would refer to the variable, and not the global alert.