端详 is a noun meaning 'detailed information' or 'particulars' — the specific facts or circumstances of a situation. It's used in formal or written Chinese, often in the pattern 端详 + (不说/不知道) or in phrases like 听端详 ('hear the details'). The dictionary also lists a 'dignified and serene' sense, but that's archaic and not used in modern Mandarin; stick with the 'details' sense for HSK 7.