This is the 5287th most frequent Russian word.
оконных
"Оконных" means "of windows" or "window-related" in English.
The term 'оконных' modifies 'рам', indicating frames belonging to or associated with windows.
Я купил краску для оконных рам.
I bought paint for the window frames.
The term 'оконные' modifies 'стекла', indicating panes designed for use in windows.
В доме установили новые оконные стекла.
New window panes were installed in the house.
Similarly, 'оконное' here modifies 'стекло', emphasizing its use in or as part of a window.