Phonetics is the study of the sounds of language. These sounds are called phonemes. There are literally hundreds of them used in different languages. Even a single language like English requires us to distinguish about 40! The key word here is distinguish. We actually make much finer discriminations among sounds, but English only requires 40. The other discriminations are what lets us detect the differences in accents and dialects, identify individuals, and differentiate tiny nuances of speech that indicate things beyond the obvious meanings of the words.