Short answers, pulled from the story.
Merriam-Webster's Online Dictionary defined truth in 2005 as the property of being in accord with fact or reality. This definition applies everyday language to things that aim to represent reality such as beliefs propositions and declarative sentences.
Philosophers discuss which entities serve as truthbearers including sentences propositions and beliefs. Sentences are concrete linguistic entities composed of strings of words while propositions are abstract entities that serve as meanings of declarative sentences. Beliefs and related mental states are concrete psychological entities taking the form of subjective attitudes about what is the case.
The correspondence theory asserts that a belief or statement is true if it corresponds to facts. This view emphasizes the relation between thought or language and reality arguing that truth matches how things are. It is one of the oldest and most influential theories of truth.
Immanuel Kant endorsed a definition of truth along the lines of the correspondence theory in his Critique of Pure Reason published in 1781. He denied that this correspondence definition provides us with a test or criterion to establish which judgements are true.
Empirical truths require sensory experience such as observing that water boils at 100°C. Logical truths can be known through pure reasoning such as a proof of a mathematical theorem and their truth is determined by the logical form of statements regardless of concrete contents.