Because coral reef terminology is so highly specialized, commonly encountered terms are introduced here, mainly with reference to eastern Pacific corals and reefs, to facilitate understanding of topics in later chapters. The distinction between coral reefs and coral communities is examined with particular attention to the coral holobiont, that is the coevolved mutualism of photosynthetic algal endosymbionts (zooxanthellae) and their scleractinian coral hosts. This ancient, coevolved symbiosis is the fundamental driver of reef development and growth. Basic coral biology and coral reef ecological processes are introduced, including growth, reproduction, predation, bioerosion, and potential environmental disturbances (e.g., ENSO anomalous warming and cooling events, upwelling, low carbonate saturation state, low tidal exposure of shallow-occurring corals, and tectonism). Reef types, their morphology, biotic zonation, and occurrence within the eastern Pacific Province are noted as well as prominent zooxanthellate coral taxa. Reef development and the characteristics of eastern Pacific reefs are briefly compared with other global coral reef regions.