What is MySQL? MySQL is a free highly reliable, scalable, fast and sophisticated Database that is before to use with Web Applications. It is one of the most highly used Web Databases available and can cater for all the needs of the vast majority of Web Application Developments. Most Web Hosting Packages include hosting MySQL or you can organise a dedicated MySQL Server or MySQL Cluster if needed. If you just starting out then a basic MySQL host included in any Web Hosting Package would be more than enough.
MySQL is based on the SQL - Structured Query Language. This language is simple to learn and includes four main commands being SELECT, INSERT, UPDATE & DELETE. Becoming familiar with SQL and MySQL will not take long and within this site you will find tutorials and code to get you going in the right direction. MySQL also integrates perfectly with PHP. You even manage MySQL from PHPMyAdmin which is a PHP Web Application developed specifically to manage MySQL Databases.
The Speed of MySQL is largely based on the speed of the Server running it. Cheap Hosting packages that include MySQL will use a shared solution potentially on cheap, lowly spec'd virtual servers which will still be more than adequate for most Web Application Implementations. If you need more grunt, which is usually only required if you have a large database with tens of millions of records then a MySQL Dedicated Server with good spec's will easily do the job. MySQL Clusters can also be provisioned and can operate across site or across the world using the SQL replication to ensure data is kept up-to-date across the entire solution.
You can store any languages from Japanese to Chinese etc that you need in a MySQL Database and the solution can handle very large amounts of data with speed. As of MySQL Version 5.1 you can partition tables allowing only the partitions with the required data to be utilised further enhancing speed. MySQL offers many different table types and data types that can be wisely chosen to further enhance performance.
PHP can be used very efficiently with MySQL and if your database calls are written with PDO - PHP Data Objects you can also avoid SQL Injection issues as the data being inserted by your users is never included on the SQL statement directly. This is essential for any Web Application in today's age because hacking is to easy and to frequent. You can learn more about PHP PDO at this page http://php.net/manual/en/book.pdo.php and will find examples of how to use this solution within this website. Take the time to learn PDO as it will save you time in the long run if your site becomes will know and used.