There are 44 basic sounds in the English language, represented by 26 letters of the alphabet. Of these, 23 are vowels, which is quite a lot more than in some other European languages, like Spanish, or Italian.
Because of the mismatch between the number of phonemes in English and the number of letters used to represent them, there are often difficulties in trying to spell English words phonetically. This is actually one of the biggest complaints of non-native speakers when they learn English.
To overcome this problem, phonetic symbols were developed to represent the natural sounds of English in a comprehensive scientific way. The International Phonetic Association has created a system that describes the phonemes which can be used not only in English, but any language in the world (even Klingon, or Sindarin!)... (For more on the schwa and other 43 English phonemes, click here.)