This document provides an overview of decision support systems (DSS) and related concepts. It defines DSS as computer-based systems that support business or organizational decision-making through the use of data, documents, knowledge, analytical models, and tools. The document discusses different types of decisions, levels of decision making, and models of decision making. It also describes the key components of a DSS, including data management, model management, user interface, and knowledge base subsystems. Finally, it outlines different types of DSS such as data-driven, model-driven, and knowledge-driven systems.