This is the 3542nd most frequent Russian word.
русских
"Русских" means "Russians" (genitive or accusative plural form).
The word 'русских' here is in the genitive plural form, used to denote possession or association with 'Russians'.
Я изучаю историю русских.
I study the history of Russians.
Here, 'русских' is also in the genitive plural form, indicating that the culture belongs to or is characteristic of 'Russian people'.
Этот музей посвящён культуре русских.
This museum is dedicated to the culture of Russians.
In this sentence, 'русских' appears in the genitive plural form, describing 'life of Russians', used in a descriptive or possessive context.