Answer:
An alphabet is what makes the written part of a language. Each letter has a certain sound that it makes (typically one). These sounds are called phonemes, or the smallest posited linguistically distinctive unit of sound.
When letters are put together, they produce different series of sounds, making words, and words (as well as rules of how and how not to use them, like 'i before e except after c' and 'never start a sentence with a conjunction'), and words make up languages.