the definition of "non-rev" means "non revenue" And, as said above, it means you are traveling for free on the airline you are employed by...or at a very big discount on another airline. You'll hear the term ID90, or ID95, etc. "ID" means "Industry Discount".
Next Flights: 12/31 AS804 PDX-MCO 2/3 AS19 MCO-SEA QX2545 SEA-PDX
One thing to to remember is that most non-rev travel is space available. That means that you only get on AFTER all revenue pax (passengers) do. Even then your priority depends on date of hire, type of pass, retired or not (lower priority than active). You might also see the term "Space Available" It's pretty self explanatory - you travel only if there is.....
Less sarcasm and more thought equal better understanding