This chapter presents an in-depth primer for the RDF Schema (RDFS 1.1) standard, which is primarily used to define a lightweight semantics for the classes and properties used in RDF graphs. After an initial motivation and overview, we discuss the RDFS vocabulary, and how it can be used to define sub-classes, sub-properties, domain and ranges, amongst other types of definitions. We then describe in detail how the semantics of RDF(S) can be formalised in a model-theoretic way, discussing key concepts such as interpretations, models, satisfiability and entailment. We introduce various semantics for RDF(S), including the simple semantics, D semantics, RDF semantics, and the RDFS semantics. We conclude the chapter by discussing how rules can be used to support entailment under such semantics.