Relational databases organize and store structured data in tables that represent relationships between entities. Tables contain rows and columns, with rows holding unique record sets and columns defining attribute types. Keys uniquely identify records and link tables, establishing relationships that are fundamental to relational databases. Relationships are created using keys and include one-to-one, one-to-many, and many-to-many associations to maintain data integrity. Relational databases also use normalization, SQL, flexibility, scalability, and ACID properties.