what they were talking about
What did they talk about?
Мне нужно знать, о чём они говорили.
I need to know what they were talking about.
Ты слышал, о чём они говорили?
Did you hear what they were talking about?
Do you remember what they were talking about?
— Анатомия падения (2023)
Интересно, о чём они говорили.
I wonder what they were talking about.