Essentially, it's a lot like real world airlines, without having to leave home all the time.
...and without being paid for flying as well. Don't lough someone asked wether virtual pilot are paid for what they do!!!
Anyway, I can add as "a new boy in town" (regarding online flying) that it is really impressive. However you have to know very well how to use navigation (VOR, NDB, enroute maps, ISD/STAR charts etc.) as well as Radio Communication procedures that is how pilots speak on their radio and what information is exchanged with the several controllers. There are plenty documents out there in VA and VACC. Another good tactic to built Radio COmmunication ability is to listen to others as they speak.
...and of course you must know how to fly well at least an airplane.