1.be known as 意为“被称作”、“被认为”:
These chocolate bars are known as something else in the US, but I can’t remember what. 这种巧克力棒在美国有别的叫法,但我记不起来叫什么了。
2.be known for 意为“因…… 而著名”:
He was known for his frankness. 他以坦率而著称。
3.be known to意为“为……所知”:
He is known to the police because of his previous criminal record. 他因以前的犯罪记录而为警察所知。
(跟famous用法差不多)