Pairs often confused
car or parce que in French?
Parce que EXPLAINS a fact and answers "why?"; car JUSTIFIES what was just claimed, and never answers on its own.
Why
To the question "Pourquoi n'es-tu pas venu ?", the only possible answer is "Parce que…". Car does not start a sentence and does not answer a question: it links two clauses, after a comma, in writing. It is more formal, and a B2 paper gains from using it once.
car
La réunion a été reportée, car plusieurs membres étaient absents.
The meeting was postponed, for several members were away.
parce que
La réunion a été reportée parce que plusieurs membres étaient absents.
The meeting was postponed because several members were away.