This is the 738th most frequent Polish word.
wie
"Wie" means "knows" (third person singular of "wiedzieć").
In this sentence, 'wie' is the third-person singular form of the verb 'wiedzieć', meaning 'to know'. It is used here to indicate the subject's knowledge about having to do homework.
Ona wie, że musi odrobić lekcje.
She knows that she has to do her homework.
Here, 'wie' again represents the third-person singular form of 'wiedzieć', used in a question format to inquire about the timing of someone's knowledge or understanding.
Kiedy on wie, co robić?
When does he know what to do?
In this example, 'wie' is used in a subordinate clause to express the third-person singular understanding, following a condition set by the main clause where the speaker ('I') doesn't know the fact.