The document discusses the field of semantics and its branches. It explains that semantics is the study of the meaning of signs and focuses on three key areas: syntax, semantics, and pragmatics. Syntax concerns properties of expressions, semantics concerns relations between expressions and what they refer to, and pragmatics concerns how expressions are used in context. The document then provides examples to illustrate semantic concepts like synonymy, entailment, contradiction, and truth conditions. It also discusses how the meaning of sentences is compositionally determined by the meanings of their parts.