Student or Learner
"Ellen soon learned the tremendous difference one's personal appearance makes in the way one is treated."
1. I have no idea which verbs is the main one, between makes and is?
2. I want to know about the meaning of this sentence.
"Ellen [subject] soon [adverb] learned [verb] ... and the rest is the direct object complement - what she learned.
What did she learn?
... the tremendous difference [that] one's personal appearance makes in the way [that] one is treated."
It could have been written:
"Ellen soon learned that one's personal appearance makes a tremendous difference in the way [that] one is treated."
(Ellen soon learned that if you look good, you're treated better.)