MySql is a relational Database Management System.
MySql Server
MySql can start on boot time or only if you type manually:
/etc/init.d/mysql start
Run mysql_fix_privilege_tables.
MySql will only install if you have a NON-NUMERIC hostname that is resolvable via the /etc/host file
["MySQL"] server creates the user debian-sys-maint that is used in the start-stop and cron ["script"]s. Don't delete him.