phpMyAdmin is a feature-rich tool written in PHP, which will give you full control over a MySQL database. You may do literally everything - set up fields, rows and tables, delete them or modify their data, export or import an entire database or just a specific part of it, and execute MySQL commands. The tool is irreplaceable in case you need to switch hosting providers, because you may conveniently generate a full backup of a database in several formats (SQL, CSV, XML). You shall end up with one file which contains the whole content of the database, so you can download it from the current provider, upload it to the server of the new one and import it via the same tool on their end. Your site shall look exactly the same, due to the fact that all script applications store their content within a database. With phpMyAdmin you could also easily search and replace content of your preference across the entire website - a word, an expression or a link, for example.