Well, it's kind of complicated, but basically voice (active, middle, passive, reflexive, pseudo-reflexive, etc.) and valency (transitive, intransitive, ditransitive, ambitranstive, etc.) are related. In nominative-accusative languages, the passive form is used to make the patient of an action into the grammatical subject of a transitive verb. (In ergative languages, there is a related form called the antipassive.) Intransitive verbs don't have passive forms. Ambitransitive verbs are those which can be used as either a transitive or intransitive verb without changing form: e.g.,
read,
break,
understand. In Romance languages, ambitransitive verbs don't tend to exist. Rather, they are replaced with pseudo-reflexive verb forms, e.g., Spanish
romperse 'to break',
olivdarse 'to forget',
hacerse 'to become, be made', etc. In English, "I broke a bone", and, "I forgot where I parked my car", though I am the grammatical subject, we tend not to think of me as the agent. I am not actively doing these things. The Spanish forms capture this in a kind of reflexive verb form: "the bone broke itself to me", "my car forgot itself to me". Real reflexives, like "I wash myself" are different in that I am both the subject/agent and object/patient.
There are also some intransitive verbs called unergative verbs which are intransitive, yet in some languages, such as Dutch, they can be passivized: "Er wordt door Jan getelefoneerd" meaning "A telephone call by Jan has been received". The flip side of these verbs are unaccusative verbs, i.e., intransitives where the grammatical subject is not perceived as the agent, e.g., English
die,
fall,
arrive, etc. In some Germanic and Romance languages, the perfect tenses of these verbs use a form of
to be with the past (passive) participle, while unergative verbs use forms of
to have: e.g., "Jan heeft getelefoneerd" ("Jan has telephoned"), "Klaas is gearriveerd" ("Klaas has arrived"), but "er wordt door Jan getelefoneerd" ("there is by Jan telephoned"), *"er wordt door Klaas gearriveerd" ("there is by Klaas arrived").
You can find many of these terms at the
Lexicon of Linguistics (at the University of Utrecht) or in
Wikipedia.
