This chapter is an overview of the Global Burden of Diseases, Injuries, and Risk Factors study (the GBD study). Section 1.1 outlines the GBD study objectives, the study history, the core indicator system, and the content of the work. Section 1.2 summarizes the eight characteristics of the GBD study: (1) comprehensive and comparability, (2) policy assessment tools, (3) a large study with multiple meta-analyses nested, (4) hierarchical structure of causes of death, disease and injuries and their sequelae, and risk factors, (5) analytical process for passing a priori distributions along a geographic cascade with DisMod-MR model, (6) data coverage continues to expand, and data are increasing rapidly, (7) a set of featured method on data quality assessment and processing, and (8) platform of Global Health Data Exchange. These features make the GBD study the only study that provides a dynamic and comprehensive assessment of mortality, disease, and risk factors in national populations in different regions of the globe. Section 1.3 provides an overview of the main statistical methods in the GBD study, including the use and development of indirect estimation methods in demographics, the development of CODEm, an integrated model for estimating causes of death, and an overview of the integrated meta-regression framework of descriptive epidemiology, Bayesian methods and Gaussian process regression, and hierarchical estimation versus population health estimation methods for small area populations, which are used throughout the GBD study. Section 1.4 provides a brief introduction to the Global Health Data Exchange platform that serves the GBD study. The overview in this chapter provides a foundation for understanding subsequent methodologies related to the GBD study.