This chapter provides an overview of some of the basic assumptions and results of phonology and phonological theory. The focus is on two main goals of phonological description and analysis: the establishment of generalizations about which members of a set of posited phonological constituents are irreducibly basic and that are derived, and the establishment of generalizations about the contexts in which phonological constituents are and are not found. These implicate four main sets of theoretical assumptions: representational assumptions about what phonological constituents are and what they consist of, analytical assumptions about the kinds of evidence that are brought to bear on the question of the basic versus derived nature of a constituent, computational assumptions about the mechanisms that relate representations of phonological constituents to each other, and architectural assumptions about how the phonological component interfaces with other grammatical components.