There are actually dozens of different varieties of coffee beans, but there are really only two that matter: Arabica and Robusta. Arabica beans tend to have a sweeter, softer taste, with tones of sugar, fruit and berries. Robusta has a stronger, harsher flavour, with a grain-like overtone and a peanut after-taste. It contains twice as much caffeine as Arabica, and is generally considered to be of inferior quality. Some Robustas, however, are of high quality and valued especially in espressos for their strong flavour and good creamy head.
Stronger, harsher flavour, grain-like overtone and peanut after-taste, more caffeine, creamier.
Sweet, with tones of sugar, fruit and berries, high acidity.