foo exists.
foo is defined.
foo has a length of 3.
foo's value is bar.
foo's Boolean value is true.

baz exists.
baz is defined.
baz has a length of 0.
baz's value is .
baz's Boolean value is false.

buzz does not exist.
buzz is not defined.
buzz has a length of zero because it is not defined.
buzz's value is undefined.
buzz's Boolean value is false.

blink exists.
blink is not defined.
blink has a length of zero because it is not defined.
blink's value is undefined.
blink's Boolean value is false.