You needn't worry about everything.
Answer:
A synonym is a word that is similar to other words, but not the same. Take the word flawed. A synonym could be defective or faulty. A vocabulary word is a word that is new to somebody and could be very prestigious and formal. For example, the word adequate could be vocabulary. Or maybe the word delectable.
P.S: If you're wondering, adequate means good or fine, and delectable means tasty or delicious.
