mysql is simply a database. It doesn't use and isn't a webserver. You use a scripting language like PHP to write SQL commands that mysql can understand. PHP can format the data in such a way as let a webserver present the information within a webpage. This is different than html as a php page can be created "on the fly" from current database contents.

Mysql can import and export data from spreadsheets. Or php can take information entered into a form and insert the data into mysql.

There is no .mysql extension that a webserver "understands".

HTH