They are set off from the rest of the sentence by a comma or commas, may have modifiers, and are not related to the rest of the sentence grammatically. You can remove them and a complete sentence remains. Transitive active verbs are the verbs in sentences with a direct object. Transitive passive verbs have the subject receiving the action with the doer in a prepositional phrase or omitted in the sentence. The verb in the transitive passive voice always has is, am, are, was, were, be, being, or been as an auxiliary or helping verb.
Intransitive verbs have no receiver of the action.
They are classified as intransitive complete or intransitive linking. Intransitive linking are sentences with a predicate nominative or predicate adjective. The man with an armful of presents tripped and fell. Into the clearing staggered the wounded soldier. The company president, Mr. Mabey, lost his temper.