This is the 2617th most frequent Polish word.
wiem
"I know."
'Wiem' is used here to state knowledge or awareness of a fact.
Wiem, że to jest trudne zadanie.
I know that this is a difficult task.
'Wiem' is used here in a negated form ('nie wiem') to indicate lack of knowledge.
Nie wiem, gdzie zostawiłem klucze.
I don't know where I left my keys.
'Wiem' appears here to emphasize personal belief or certainty in motivation.