"Nothing", used as a pronoun, is the absence of a something or particular thing that one might expect or desire to be present or the inactivity of a thing or things that are usually or could be active. As a predicate or complement "nothing" is the absence of meaning, value, worth, relevance, standing, or significance.

What is meaning of nothing really?

1 indefinite no thing; not anything, as of an implied or specified class of things. I can give you nothing. 2 no part or share. to have nothing to do with this crime. 3 a matter of no importance or significance.

What does nothing but true mean?

The absolute truth about something, without omission, embellishment, or alteration. Used to swear in witnesses while giving evidence in court, and used by extension in other contexts.