not know what's what

基本解释

"That boy is suffering for society and fun, " she said to herself. "His grandpa does not know what's good for him, and keeps him shut up all alone.
“这个小伙子没有朋友，没有欢乐，”她心里说，”他爷爷不知道他需要什么，总是把他孤零零地关在屋里。
When I was a kid, we watched a popular TV show entitled, Father Knows Best. Your earthly father may not always know what's best, but your heavenly Father does.
我小时候，看过一个很流行的电视剧，叫《老爸大过天》（Father Knows Best）你在地上的父亲不会总是知道什么是最好的，但你的天父可以。
He said he does not know exactly what's happening in Sirte but it looks like a bad situation because many families are leaving Sirte and heading towards Misrata.
亚米德说，他不知道苏尔特究竟发生了什么事，但看起来情况很糟，因为很多家庭都要离开苏尔特到米苏拉塔去。

Some people might not have firm plans yet for New Year's Eve, but others know exactly what they will be doing.
Usually when you know why it's not working, it's obvious what you have to do to make it work.
通常你明白了出错的原因后，很明显你必须让程序正常运行起来。
麻省理工公开课 - 计算机科学及编程导论课程节选
So, if we have a high intensity, we're talking about having more photons per second, and it's important to know also what that does not mean.
所以，如果我们有一个高强度，我们就是在讨论每秒钟,有更多的光子数，同样理解它不代表什么,也是很重要的。
麻省理工公开课 - 化学原理课程节选

Third, we urged states to use cutting-edge data systems to track a child's progress throughout their academic career, and to link that child's progress to their teachers so we know what's working and what's not working in the classroom.
WHITEHOUSE: Race to the Top for Education Reform