Ali eve gelmişti.
English: Ali had come home.
In Turkish, 'iç içe geçmiş zamanlar' means using more than one tense together in a sentence, especially to talk about actions that happened before another action in the past. This is often called 'reported past' or 'past within the past.'
You use these forms to talk about an action that was already finished before another past event, or to report something that had happened earlier. It's common in stories or when giving background information.
Ali eve gelmişti.
English: Ali had come home.
Sen aradığında ben çoktan çıkmıştım.
English: I had already left when you called.
Film başladığında herkes yerini almıştı.
English: Everyone had taken their seat when the movie started.
Ders bittiğinde ödevimi bitirmiş olacağım.
English: I will have finished my homework when the class ends.