This is the 2303rd most frequent Russian word.
лесах
"Лесах" means "forests" in the prepositional or dative plural form.
Here, "лесах" is used in the prepositional case plural form of "лес" to indicate location within forests.
Мы гуляли в густых лесах.
We walked in the dense forests.
In this sentence, "лесах" serves as a prepositional case plural of "лес" to describe attributes of the forests as a location.
В этих лесах много медведей.
There are many bears in these forests.
Here, "лесах" is used in the prepositional case plural to indicate the topic or subject related to forests.