There are quite a few roles that these cords play. The main function is that when it vibrates and the air goes through the cords, it produces a sound which we call voice. This air goes through the lungs to make a sound. When we are silent, they are relaxed letting air flow through, but when they are tight, less air flows through; the tighter they are, the higher your pitch is. In the article above, we have seen the vocal cords diagram. Using that you can easily understand its functions. In simple terms, the main function is to produce sounds.