background, true nature, full story
闫先生已经知道我底细了
Mr. Yan already knows all about me.
— 唐人街探案 (2015)
不会是我一个人的我很清楚这两人的底细
It can’t be just me. I know these two inside out.
— 野蛮入侵 (2003)
我知道你的底细
I know what you're really like.
— 搏击俱乐部 (1999)
你也许知道我们是谁我们可清楚的知道你的底细，懂吗？
You may know who we are, but we know exactly what you're all about, got it?
— 好家伙 (1990)