A relational database is a type of database that organizes data into tables, which consist of rows and columns. Each table represents a different entity, such as customers or products, and the relationships between these tables are defined using keys. This structure allows for efficient data retrieval and management, making it easier to maintain data integrity. Data in relational databases can be accessed and manipulated using a language called SQL (Structured Query Language). SQL allows users to perform various operations, such as querying data, updating records, and creating new tables. This flexibility makes relational databases popular for applications in various fields, including business and finance.