This is the 2nd most frequent Spanish word.
que
"Que" means "that," "which," "who," or is used as a conjunction or question word depending on context.
In this sentence, "que" is used as a conjunction to introduce a subordinate clause that provides additional information about the main clause.
Yo sé que tienes razón.
I know that you are right.
In this case, "qué" is an interrogative pronoun employed in formulating a direct question to ascertain specific information.
¿Qué quieres comer hoy?
What do you want to eat today?
Here, "que" serves to introduce a relative clause that specifies or defines the action in the main clause.