This document provides an overview of health information systems. It defines key terms like health information system and routine health information system. It describes the six components of an effective health information system according to the HMN framework: governance and leadership; data sources; data management; information products and dissemination; data quality; and data use. It also discusses data collection instruments, indicators, data quality dimensions, and characteristics of a strong health information system. The document is intended to teach participants about health information systems and their essential role in supporting decision-making across health system levels.