Nagios Plugins
Plugins are basically scripts of Perl and Shell that can be run through the command line to check the service status of the host. Nagios can also use the result of the plugins that determine the present status of host or services of the network.
Now an answer to the questions that why we need plugins, you can also add here that, plugins is executed by Nagios to check the status of any service or host. A check is performed by the plugin and the result is returned to Nagios. The result is processed by Nagios to take the necessary actions.
