When studying the vowels in a language, it's important to understand how they are produced and how they function within that specific language's sound system. The classification and number of vowels can vary widely depending on the language being studied. Vowels are speech sounds that are produced without any significant constriction or closure in the vocal tract. They are typically voiced, meaning the vocal cords vibrate when producing them. Vowels can be classified by their height, backness, and roundness, and also by whether they are tense or lax.