There are two primary types of coffees. The first, and most commonly found category is the Cafe Arabica. Historians claim that the arabica species was the first to be cultivated and brewed.
The plant itself has white flowers, and the beans range from red to purple in color. This was the bean that was found in Ethiopia and exported to Southern Arabia, hence the etymology becomes clear.
The second type of coffee is the Cafe Robusta. The Robusta strain was first found in mid-western Africa. The Robusta has a much higher crop yield than the Arabica, and also is higher in caffeine content.
The Arabica beans have a sweeter taste to them, and are milder in flavor than the Robusta. The Robusta is fuller, but also more bitter. The Robusta has a grain overtone, which is a given since it grows in harsher conditions.
The Arabica has subtler flavors, and stimulates the whole palate. Arabica is also much harder to grow than the Robusta strain, and this is precisely why the former is more expensive than the latter.
The Arabica has higher acidity, and has pleasant notes of fruit, chocolate and nuts. The Robusta has a burnt, almost woody taste to it and is harsher when compared with the Arabica.
There is also the lesser known cousin of these beans called Cafe Liberica. The Liberica beans hail from the Philippines, and have a much lower yield than both Arabica as well as Robusta.
Liberica beans have a smoky flavor, and also have fruity and nutty notes, and are a good coffee bean on its own. Since the Liberica is only grown in Philippines and also gives a good, fruity as well as a robust body, it is on the pricier side.
The last type of coffee bean is the Excelsa bean. This bean is a derivative of the Liberica, and can be found in Southeast Asian countries.
The Caffeine content on this bean is low, and the coffee is paler and light. The beans leave a fruity note with very little bitterness that is associated with coffee. These beans make up only about 7% of the coffee production.