What's the difference in Robusta coffee beans and Arabica coffee beans?

Rubosta (Coffea Canephora) has a 2% of caffeine content. while Arabica (Coffea Arabica) has only 1% of Caffeine. When it becomes into its variety cultivation, the Arabica is a Self-Pollination, while the Rubosta is Cross-Pollination, and that may cause to leverage the caffeine level content of Rubosta. The biggest producer of Arabica; Brazil and Columbia, while the Rubosta; Vietnam and Indonesia.