This is the 15019th most frequent Russian word.
подушку
"Pillow."
Here, 'подушку' is used in the accusative case indicating the object of the verb 'купил' (bought).
Я купил новую подушку для сна.
I bought a new pillow for sleeping.
Here, 'подушке' is in the prepositional case, showing the place of action ('resting on the pillow').
На этой подушке очень удобно отдыхать.
It's very comfortable to rest on this pillow.
In this sentence, 'подушку' is in the accusative case as it is the object of the verb 'дали' (gave).