A relational database is a type of database that stores and provides access to data in tables, relating data in one table to similar data in another table. Relational databases have been around since the 1970s, are used in various use cases, and remain popular due to their mature, stable, and proven technology. They offer a structured view of the world, fitting well with modeling real-world business entities and relationships. SQL statements are often simple enough to be human-readable, and lower the barrier to entry for application developers. Relational databases provide data integrity through ACID guarantees, ensuring atomicity, consistency, isolation, and durability. They support various scalability options, including vertical and horizontal scaling, and offer flexible pricing models. However, relational databases come at a cost of limited flexibility and performance compared to non-relational systems. Document-relational databases like Fauna combine the benefits of relational and non-relational systems, offering flexibility, performance, and querying and transactional guarantees without compromising simplicity and scale.