The Nerd doesn’t mean to be critical. But it’s technically true that Hebrew vowels are “diacritical marks” (Google it). You see, Hebrew originally had no vowels (and modern Hebrew doesn’t use them either). Rabbinic scribes (Masoretes) in the early Middle Ages worried people would forget how to pronounce Hebrew. But they did not want to add letters to the sacred text. So they used markings below and above the letters instead. Now, here are some flashcards and the Nerd will try and make it easy for you.