What is a challenger brand?

In essence a challenger brand is a product or service that comes along and disrupts the status quo, it does things differently and if successful changes how a whole industry approaches things. Also described as change makers.

For example Airbnb completely changed accommodation - Prior to Airbnb options for travel were hotels and guest houses, or specialised agents for booking an apartment. In its original incarnation Airbnb worked as as hook up for people to go sofa surfing, or kip in someone's spare room but as it's success grew it is mainly now used for people to offer apartments and whole properties for use. 

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