What is the meaning of S-IV sentence pattern?

The S-Iv pattern.the simplest of sentence patterns is composed of a subject and verb without a direct object or subject complement. It uses an intransitive verb, that is, a verb requiring no direct object.S stands for subject and Iv for intransitive verb.e.g.1.) Mr. Potato Head eats monkeys.2.) I refuse.3.) She sleeps every afternoon.