What is known和It is known还有就是It seems和What seems有什么区别啊？

What is known和It is known还有就是It seems和What seems有什么区别啊？

what is known as意思是“大家所熟悉的，所谓的
He’s what is known as a “bellyacher” —— he’s always complaining about something.
他是大家所熟悉的一个爱发牢骚的人，他总是抱怨。
It is known放在句子开头，是众所周知的意思，相当于pepole know that...
It is known that computers, one of the greatest inventions in the human being’s history, are widely used in our everyday life.
众所周知计算机是人类历史最伟大的发明之一，在我们的每日生活中被广泛的使用。

It seems to me 是对我来说，在我看来，我觉得。。。
It seems to me that we will have a warm winter.我觉得今年会是一个暖冬。
it seems that:似乎..., 看来好像...
It seems that she is ill.
她似乎病了。

It seems that it is going to rain.
仿佛天要下雨。

what seems 后面可以加形容词，意思是什么似乎是怎么怎么样的？
What seems to be...这种表达方式用的多。意思是...似乎是什么..
What seems to be the problem? 哪出毛病了?
What seems to be the problem is that S + V...问题似乎是…

What is known是一个名词性从句,在句中做主语或者宾语，相当于一个名词,是“众所周知的事情”的意思
it is known 是一个主语从句，后面接that从句，it表示that从句的内容，表示。。。。是众所周知的。
it seems又是一个主语从句，后面可以接adj。或者that从句，表示好像。。。
what seems要根据具体情况而言，但总体上还是相当于一个名词，“好像。。。的事情
例如：what seems awful is coming.貌似可怕的事情将要到来。