Korean grammar patterns explained with real examples
Both get translated as "but," but only -지만 is really a contrast. -는데 sets the scene for what comes next — here's how to hear the difference.
Textbooks say 은/는 is the "topic marker" and 이/가 is the "subject marker." That tells you nothing. Here is the rule that actually works.
You can recite the 하다 rules and still freeze mid-sentence. The gap is between recognising a form and producing one under time pressure.