Well- known通常指较小的圈子，或处于特定情况下的人，但仍然为很多人所熟知。Famous可以指某人或某事，意思是很多人知道他们/它的名字或听说过他们/它。名人Celebrity通常用来指非常有名的人，即a famous person。
用英语解释：
Well-known means someone or something is known by many people or by the people involved in a particular situation.
If someone or something is famous, a lot of people know their name or have heard about them。
Famous的字典解释：
Having a widespread reputation, usually of a favorable nature;
renowned; celebrated: a famous writer.
例句：
Have you ever dreamed of becoming a famous writer?
The picture of Mona Lisa's smile is the world's most famous picture.
well-known的字典解释
clearly or fully known: The well-known reasons are obvious.
generally or widely known: a well-known painting.
Well-known与famous类似，都有“著名”的含义，然而它也描述了某个特定群体中的人。
例如，你可以说你们学校的校长在学校很有名。他/她是校长，所以每个人都认识他/她。你不能用“famous”这个词，因为你们城市以外的大多数人可能都不在乎你们学校的校长。
例如：
I’m from a well-known country.
You are a well-known lawyer.
“Famous”通常用来描述一个很多人都认识的名人或重要人物。但famous并不一定都是褒义，有时也可能因名声不好而绯闻天下。这时候较好的一个词是popular。Popular就是赢得很多人的心。一个popular的人会被成千上万的人喜欢。但famous不是一回事。Famous只是被很多人熟知。一个有名的人可能被成千上万的人知道，但这并不意味着他是被喜欢和爱的人。以一个政治家为例。他可以出名，但不受欢迎。然而，当一个人很受欢迎时(popular)，他自然也会出名。
举例来说famous:
Hitler was famous throughout the world and even today his name is known by most of us.
通过这个例句可看出一个人出名不一定要投身于有价值的事业;他甚至可以是邪恶的或具有破坏性的。
