Router filter - difference between "Exists" and "is not empty"

Does the "Exists" filter refer to the label itself and "is not empty" filter referring to the field/value? Same logic for "Does not exist" and "is empty"?

Exists means the key:value pair exists, it can be empty but it is available to match/check.

Is Not Empty means value of the key is not blank, there is something as a value.