This is the 18th most frequent Slovak word.
čo
"What."
In this sentence, "čo" works as an interrogative pronoun used to ask about someone's name.
Čo je tvoje meno?
What is your name?
Here, "čo" functions as a relative pronoun connecting the two clauses, indicating the object of thought.
Neviem, čo si myslíš o tomto filme.
I don't know what you think about this movie.
In this case, "čo" serves as a conjunction that introduces a defining relative clause, providing additional information about "všetko".