This is the 173rd most frequent Polish word.
czym
The Polish word "czym" means "what" or "with what" and is used as an instrumental case form of "co."
The word 'czym' is used as an instrumental case form of the pronoun that means 'what', acting as an interrogative word asking about the subject of activity.
Czym zajmujesz się na co dzień?
What do you do daily?
Here, 'czym' is part of a question comparing two entities, again taking the instrumental case form of 'co' to specify the means or object of comparison.
Czym różni się ten produkt od tamtego?
How does this product differ from that one?
'Czym' is utilized here to indicate the means or reason behind the action, derived from 'co' (what) in the instrumental case.