What is the highest earning app in the world?

I'm curious, could you please shed some light on what is currently considered the highest earning app in the world? Is it a game, a productivity tool, or perhaps something entirely different? I'm fascinated by the financial success of mobile apps and would love to know more about the one that tops the charts in terms of revenue generation. Could you also elaborate on any notable factors that have contributed to its success, such as its unique features, marketing strategies, or the target audience it caters to?