Commentary explaining the meaning of the ayahs. One passage often covers several ayahs, so neighbouring ayahs can show the same text.
Tafsir Al Jalalayn - English tafsir for Surah Al-Muddaththir — Ayah 27
وَمَآ أَدۡرَىٰكَ مَا سَقَرُ ٢٧
And how would you know what is Saqar? — this [interrogative] is intended to emphasise its enormity.