This is the 55th most frequent Polish word.
nas
"Nas" in Polish means "us" in English.
In this sentence, 'nas' functions as the direct object, the recipient of the action 'odwiedzają'.
Oni odwiedzają nas co roku.
They visit us every year.
Here, 'nas' operates as part of the prepositional phrase 'o nas', referring to a topic or subject of memory.
Czy możesz o nas pamiętać?
Can you remember about us?
In this case, 'nas' serves as part of a prepositional phrase 'dla nas', indicating a beneficiary of the importance.