IPA: /ˈθiːətərˌɡoʊər/
KK: /ˈθiːətərˌɡoʊər/
A person who regularly goes to see plays, movies, or performances at a theater.
As a theatergoer, she enjoys watching new plays and classic performances.
The word 'theatergoer' is formed from 'theater' (from Greek 'theatron', meaning a place for viewing) and 'goer' (from Old English 'gān', meaning to go). A theatergoer is someone who goes to a place for viewing performances, particularly plays or movies.
Think of someone who 'goes' ('gān') to a 'place for viewing' ('theatron') — that's what a theatergoer does.
No commonly confused words.