Demonstrative noun phrases (e.g., that guy, this) are of interest to philosophers of language and semanticists because they are sensitive to demonstrations or speaker intentions. The interpretation of a demonstrative therefore sheds light on the role of the context in natural language semantics. This survey reviews two types of approaches to demonstratives: Kaplan's direct reference treatment of demonstratives and other indexicals, and recent challenges to Kaplan's approach that focus on less obviously context-sensitive uses of demonstratives. The survey then covers selected research on demonstratives in linguistics. This research offers new empirical puzzles and contrasting theoretical approaches to demonstratives.