"Espresso" is not a term given to a type of bean, or even to a kind of roast process. Rather Espresso relates to a type of coffee drink- a bevage made using a particular type of machine which extracts the coffee in a certain period of time (around 25 seconds) under pressure. Many retailers advertise they sell "espresso blends"... which by definition are the blended coffee beans they use for their espressos. There is not such a thing as a true general espresso blend... for instance I have seen espresso's roasted from very light, to very dark. The blend itself can be variable. In many parts of Europe the blend is almost entirely robusta, while in the states, Australia and Asia it can be anywhere from a high % of robusta to an Arabica rich blend. The important thing is how the espresso looks, tastes and smells once it has been prepared. As the SCAA says- it should "have the viscosity of warm honey and the resulting beverage will exhibit a thick dark golden red cream-foam ("crema")." The taste will vary, but as OE alluded to in Espressoforums... it should not be bitter or hard on the pallate....rather mellow, pleasant, nutty.....