Ali kitabı okuyor.
English: Ali is reading the book.
In Turkish, 'etken çatılar' (active voice) is when the subject of the sentence does the action. The subject is the 'doer'.
Use the active voice in Turkish when you want to show clearly who is doing the action. It is the most common way to make sentences in Turkish.
Ali kitabı okuyor.
English: Ali is reading the book.
Ben kahve yaparım.
English: I make coffee.
Öğrenciler soruyu cevapladı.
English: The students answered the question.
Ayşe meyve satın aldı.
English: Ayşe bought fruit.
Biz film izledik.
English: We watched a movie.