The vast, vast majority of coffee produced and consumed in the specialty coffee industry is of the species Coffea Arabica. There are lots of varieties of Arabica, such as Bourbon or Typica, but Arabica only accounts for around 70% of the coffee consumed around the world: there are as many as 100 other species of the Coffea genus.
The next most consumed species is called Coffea Canephora, generally known by its only cultivated variety, Robusta. It makes up about 30% of global coffee production, grown mainly in Central and Western Africa, Southeast Asia, and in Brazil.
Robusta has a much heavier and richer flavour profile than the more delicate and aromatic Arabica. In fresh coffees, it is normally blended with Arabica to give extra body and oomph. As an espresso, it produces a thick, unctuous crema, so is often added to espresso blends in small quantities to boost the texture.
Robusta is a much more hard-wearing, disease resistant plant than Arabica – hence the name. Its trees are also just plain bigger. It can also handle warmer weather, meaning it can be grown in many more regions than Arabica, particularly south of the so-called “coffee belt”, and at lower altitudes than the pickier Arabica.
All this means that Robusta is a much cheaper crop to grow, with lower risks attached. Robusta is particularly popular for instant coffee, where the reliability and low cost of the crop far outway the quality concessions. It also has about 50% more caffeine than Arabica, which is the main reason we drink instant coffee anyway.