"They are knowledgeable" is a common expression to describe someone who is well-informed or has a lot of knowledge.
This expression comes from the word "knowledge", which means to have information or understanding about a particular subject or situation.
Example sentences in Engpsh with Chinese translation:
"She is knowledgeable about art and can easily identify different styles and techniques."
她对艺术有很深的学问，能轻松地识别不同的风格和技巧。
"John is knowledgeable about many different topics and always impresses people with his insights."
约翰对许多不同的话题都有学问，总是令人惊讶他的见解。