MySQL
In plain terms
A widely-used open-source relational database.
Going deeper
MySQL is a popular, reliable SQL database powering countless web applications, known for speed and ease of use. It's a staple of the classic web stack.
Under the hood
Multiple storage engines (InnoDB for transactions); owned by Oracle, with MariaDB as a community fork.
Examples
WordPress, web apps, the LAMP stack, e-commerce, MySQL/InnoDB.
Think of it like...
Like a dependable, popular filing system that runs much of the web.