The structure of 能说会道 is one of repetition for emphasis. It combines “can speak” (能说) with “skilled at talking” (会道) to create a powerful image of someone with complete mastery over their words. They don't just speak, they do it with skill and capability.
In Chinese culture, eloquence (口才 - kǒucái) has long been a highly valued skill. From ancient scholars advising emperors to modern-day business leaders negotiating deals, the ability to speak persuasively is seen as a key indicator of intelligence and capability. Being described as 能说会道 is often a significant compliment, especially in professional fields like law, sales, and public relations. However, there's a cultural nuance that differs from the Western concept of being “articulate.” While “articulate” is almost exclusively positive in English, 能说会道 can be tinged with suspicion. It can sometimes raise the question: Is this person genuinely wise, or are they just a “smooth talker” using clever words to mask a lack of substance or sincerity? This reflects a traditional value that sometimes prioritizes quiet action over eloquent speech. So, while it's similar to “having the gift of the gab,” it can sometimes carry the same slight warning as “slick” or “silver-tongued.”
能说会道 is an extremely common idiom used in everyday life. Its connotation depends heavily on the context and the speaker's tone.