MySQL is an open-source relational database management system (RDBMS). It is based on Structured Query Language (SQL) and is used for managing and organizing data in databases. MySQL is widely used in web applications and is known for its reliability, ease of use, and performance. It supports a variety of operating systems and can handle large databases efficiently.

MySQL was originally developed by a Swedish company, MySQL AB, which was later acquired by Sun Microsystems and subsequently by Oracle Corporation. MySQL uses a client-server model, where the server manages the database and the clients connect to the server to perform tasks such as querying and updating data.

One of the key features of MySQL is its support for various storage engines like InnoDB, MyISAM, and Memory, each having different characteristics and use cases. InnoDB, for example, supports transactions and foreign keys, making it suitable for applications requiring high reliability.

MySQL is also known for its robust security features, including user authentication, data encryption, and secure connections. Additionally, MySQL provides tools for backup, recovery, and replication, which are essential for maintaining data integrity and availability.

Many popular websites and applications, such as Facebook, Twitter, and YouTube, use MySQL to manage their data due to its scalability and performance.