This is the 59th most frequent Portuguese word.
esse
"Esse" means "that" (used for something close to the listener) or "this" (depending on context).
In this sentence, 'esse' is used as a demonstrative adjective to refer to a nearby object (perhaps in a conversational context close to the listener).
Esse livro é interessante.
This book is interesting.
Here, 'esse' again serves as a demonstrative adjective, denoting a movie that was possibly mentioned before or is related to the immediate context of discussion.
Eu vi esse filme ontem.
I watched this movie yesterday.
'Esse' in this instance points out a specific man, suggesting that the man is a subject of focus or is close to the listener.