In linguistics, specifically phonetics and phonology, schwa (/ʃwɑː/, rarely /ʃwɔː/ or /ʃvɑː/;[1] sometimes spelled shwa)[2] is a vowel sound denoted by the IPA symbol ⟨ə⟩, placed in the central position of the vowel chart. In English and some other languages, it represents the mid central vowel sound (rounded or unrounded), produced when the lips, tongue, and jaw are completely relaxed, such as the vowel sound of the ⟨a⟩ in the English word about.
Reference: https://en.wikipedia.org/wiki/Schwa