MySQL is an open-source relational database management system that uses Structured Query Language (SQL) for accessing and managing data. It is widely used for web applications and is known for its reliability, ease of use, and flexibility. MySQL can handle large amounts of data and supports various platforms, making it a popular choice for developers. MySQL is often used in conjunction with other technologies, such as PHP and Apache, to create dynamic websites and applications. It allows users to store, retrieve, and manipulate data efficiently, making it essential for many online services and software solutions.