The document discusses deixis and definiteness in language. It defines deixis as words that take meaning from the context of an utterance, such as personal pronouns and spatial/temporal indicators. Definiteness refers to a speaker assuming a hearer can identify a noun phrase's referent. Common definite noun phrases include proper names and those introduced with a definite determiner. The extension of a predicate is the set of all potential referents, while sense is the linguistic meaning and reference connects language to specific real-world entities.