MySQL is an open-source relational database management system, developed, distributed and supported by Oracle Corporation. A relational database stores data in separate tables of rows and columns, and the database enforces rules about how the tables relate, for example that each order points to an existing customer.
An application connects to the MySQL Server and sends queries in SQL (Structured Query Language), the standard language for reading and changing data in a database. It does this directly or through a connector, a library for a programming language that talks to the server. The server stores the tables in files organized for speed. It supports replication, which keeps copies of the data on other servers, clusters of servers with InnoDB Cluster and NDB Cluster, and use as a document store. It can also run on an ordinary desktop or laptop, next to other applications.
The MySQL Community Server is free to download and use under the GPL (GNU General Public License). Oracle also sells commercial licenses, the paid MySQL Enterprise Edition with extra tools and support, and the MySQL HeatWave cloud service.