This is the 7th most frequent Ukrainian word.
про
"Про" in Ukrainian means "about" or "concerning."
In this sentence, "про" indicates the subject or the theme of the book being about travels.
Я прочитав цікаву книгу про подорожі.
I read an interesting book about travels.
Here, "про" refers to the topic of the conversation, specifically plans for the weekend.
Ми говорили про плани на вихідні.
We talked about plans for the weekend.
In this instance, "про" specifies the central theme or focus of the movie being about friendship.