MySQL is an open-source relational database management system (RDBMS) that is often used to store and manage data on a website or other application. MySQL is one of the most popular database management systems in the world and is used by many large companies such as Facebook, Twitter and YouTube.

MySQL allows users to store data in tables and retrieve and update it using a query language. MySQL's query language is called Structured Query Language (SQL) and is a standardised language used by many relational database management systems.

MySQL offers a variety of features, including data security, scalability and flexibility. It is also highly customisable, so it can be easily integrated into many different types of applications and platforms. There are also many third-party tools and extensions that can extend the functionality of MySQL and customise it to specific requirements.