Many years ago when she was studying for the TOEFL exam, my wife asked me to explain the difference between a main clause and a subordinate one. She somehow had it in her head that as a native speaker I would instinctively know what those words meant.
At the time, she had yet to learn that the only thing instinctive about her new husband was his ability to blink. Still, I was able to grope deep within my gray matter and yank out the following definition:
"It's sort of like our marriage. Here, I am the main clause and you are the subordinate."