Strangely enough, alert variables are one of the more straightforward features to configure in Orion's alerting engines.  Although they may seem a little confusing at first, they're really just a way to include relevant information in the messages that are sent when an alert is triggered or reset.  That's it.  These messages could be one of a number of things, like messages sent to the event log, or an email that's triggered when the alert fires.  That said, let's walk through the steps of configuring variables in an alert message.

When creating alerts in the Alert Manager, you can specify variables on the 'Trigger Actions' tab.

Here you can see we have two messages that will trigger when the alert fires: one to the event log, and an email.  Let's take a look at the event log message.

Here, we have specified the contents of the message to be written to the event log using two variables: ${NodeName} and ${Status}.  When the proper trigger conditions are met, an alert will fire that will write a message to the event log, and the message will tell us which node is affected as well as the status of the node. You can also specify variables in the same way when configuring an email to be sent when the alert triggers.

I'd also like to share a hint.  Not all of the variables available to you are displayed in the variable list in the Alert Manager.  For a complete list of variables, check out the appended Administration Guide which is posted here.