The "Conditionnel Passé" is a French verb tense used to express actions that would have occurred in the past under certain conditions. It is formed using the auxiliary verbs avoir or être in the conditional present, followed by the past participle of the main verb. For example, "J'aurais mangé" means "I would have eaten." This tense is often used in hypothetical situations or to express regret. For instance, "Si j'avais su, je serais venu" translates to "If I had known, I would have come." The "Conditionnel Passé" helps convey what might have happened differently in the past.