I teach English, not German, so please keep that in mind, but I believe I can clarify this question since it had been a question of mine awhile ago.
The two words are not really the same. While they can both carry several meanings, “betreffen” primarily means “to affect” while “treffen” primarily means “to meet.”
„Das würde mich betreffen.“ ← That would affect me.
„Wir werden uns im Café treffen.“ ← We will meet each other in the cafe.
I hope this helps.