mysql.server is a script that starts and stops the mysqld server by invoking mysqld_safe (or safe_mysqld, depending on your version of MySQL). mysql.server is a shell script and is unavailable on Windows. It was introduced in MySQL 3.22.7.
Normally, mysql.server is used on a System V-style system and is installed in one of the runtime directories under the /etc directory. The system starts the server by invoking the script with an argument of start at system boot time. The system shuts down the server by invoking the script with an argument of stop at system shutdown time. The script can also be invoked by hand with the appropriate argument to start or stop the server.