This is the 12882nd most frequent Russian word.
левую
"Левую" is the accusative form of "левая," meaning "left" (referring to the left side).
In this sentence, 'левую' is used as an adjective describing the street, which is on the left side.
Я повернул на левую улицу.
I turned onto the left street.
Here, 'левую' modifies 'сторону' (side), indicating preference for the left side.
Он всегда выбирает левую сторону для прогулок.
He always chooses the left side for walks.
'Левую' colloquially means 'wrong' or 'fake' in contexts like transactions, describing incorrect change received.