What is the 'future in the past' in Italian?

The 'future in the past' is a grammatical concept in Italian that doesn't exist in English. We use it to talk about things that, in the past, we thought might happen in the future. Sounds confusing? An example sentence in English might be, 'I was sure that she would understand.' In English, we use the present conditional to talk about what we thought she would do. In Italian, however, we would use the past conditional to do so - making the translation 'Ero sicuro che avrebbe capito.' However tempting it might be, don't say 'Ero sicuro che capirebbe' - it may be a direct translation of the English, but in Italian it's incorrect. In spoken, colloquial, Italian, it's also common to simply use the imperfect 'Ero sicuro che capiva' - but don't write this in essays!