What is the difference between Arabica and Robusta beans?

Arabica beans tend to have a sweeter, softer, taste, with the tone's of sugar, fruit, and berries. Their acidity is higher, with that winey taste that characterizes coffee with excellent acidity.
Robusta beans have a stronger, harsher taste with a grain like overtone and a peanutty aftertaste. They contain twice as much caffeine as Arabica beans. They are generally considered to be of an inferior quality compared to Arabica. Some Robusta beans are of higher quality and valued especially in espressos for their deep flavor and good crema.