A star schema is a type of dimensional model that is used to organize and store data in a data warehouse. It is based on the idea of organizing data into a central fact table surrounded by dimensional tables. The fact table contains quantitative data, such as sales and profits, while the dimensional tables contain descriptive attributes, such as customer and product information. The star schema is designed to support fast querying and analysis of data, particularly in the context of online analytical processing (OLAP).