The exclamation marks delimit arguments to the command line - $ARG1$ is the first equal to 1, $ARG2$ is the second equal to 2.
In order to understand exactly what this command does you will need to check the host it is checking. check_nrpe is used for doing remote checks.
Locate the config file (usually at /etc/nagios/nrpe.conf or similar). The line that defines check_jdbc_conn should be listed. Once you understand what the remote plugin is doing everything should be clear.