One of the purpose of the pre-flight briefing is safety. The captain can ask some questions, the cabin crew will answer. Besides, flights are not the same, that's why you may need some special information about the flight and something unusual. Takeoff, departure, approach and landing conditions (e.g., weather, runway conditions, special hazards) should be taken into consideration. Moreover, briefing can enhance the preparedness of the flight crew and cabin crew for facing unusual requirements or responding to unexpected conditions.
Авиационный английский по скайп, помощь в подготовке на уровень ИКАО, SELCAL - запись на уроки.