A schwa is a weak sound of any vowel. The stress in a word is on other syllables, but never on the syllable where the schwa is. The schwa is the unstressed sound of a vowel in a word, which is vaguely heard.
A syllable is a small word like the word me, or a part of a word like the syllable me in me•di•a.
Vowels rule English and they cannot be avoided. Vowels are inconsistent; each vowel has a short sound, a long sound, and a number of other sounds. Vowels are the strong letters and consonants are the weak letters. Consonants often double to preserve their sounds, as in class.