An airline hub is an airport where the airline has a heavy presence and normally some kind of headquarters. On the other hand, a focus city is a destination where the airline operates limited point-to-point routes. In these cities, the airline doesn’t necessarily need to have an office (even though this sometimes is the case). Many low-cost airlines don't use the definition 'hub' but instead define their main airports of operations as an operating base.
IATA Code: WW
ICAO Code: WOW