The Subjunctive mood expresses doubt, uncertainty, hope, fear, possibility, opinions, etc. and is used much more frequently in Italian. It is mainly used in dependent clauses (sentences introduced by a conjunction that do not have a complete meaning) that are introduced by che.
The "congiuntivo" is also required with particular expressions such as:
Italian subjunctive has four forms. The two first ones (Present and Imperfect Subjunctive) are simple tenses, with their own inflections:
And the last compound tenses (congiuntivo passato and congiuntivo trapassato) are made in the same way as the indicative ones (auxiliary verb + past participle of the main verb), though the two auxiliaries essere and avere use subjunctive inflections.