In addition to the great responses above, you will see IFC people use VA (Virtual Airline) and VO (Virtual Organization) interchangeably. A VA is often modeled after an airline with routes, ranks, and more stringent rules. A VO sometimes may be a club or organization that provides a service. Refueling, general aviation club, military protection, etc. But in terms of your profile any VA or VA may be selected in the box to be shown in the sim.
The honor system is utilized as there is currently no master database of every user and va/vo they are apart of. (This data often changes rapidly) Please only select what you are actually a part of to help everyone out.