It is made differently than “normal American-style coffee”. If you try to make a cappuccino from coffee grounds, it may have a weak, flat taste due to the improper method of preparation. The espresso grounds have a darker roast to give the beer a smokier flavor, and they are also finely ground. Normal coffee beans can be roasted in a variety of ways, from light to dark, and are usually ground to medium for a drip coffee maker.
If you are using a French press brewing method, the coffee grounds will be crushed into large pieces. Grind: Finely ground coffee beans are a favorite for espresso because fine grinding creates a delicious cream. The perfect grind size for espresso ground coffee should be as fine as sand. Fine grinding is vital to the espresso making process because they absorb the pressure forced by hot water.
The difference is in how you do it. In short, espresso is an Italian-style coffee made with high pressure and speed. You need a uniform grind size and a special machine to make a good espresso. In comparison, other types of coffee are usually prepared by slowly filtering water through the coffee grounds.
But espresso is just one of the methods for brewing coffee among many, from pouring to the French press and siphon coffee makers. While manual grinders like Hario Skerton are convenient for grinding some grains into pouring, they struggle to produce a grind size that is fine and even sufficient for espresso. Walk into any coffee shop in Italy and order an espresso, and you'll get just what you expected: a small, strong shot of coffee with a layer of cream on top. The couple of times I tried beans prepared for espresso in a French press they gave me a rough, bitter cup of coffee, so I don't recommend it.
The coffee grounds suitable for preparing espresso are finely ground, while those ground for a paper filter are medium to medium-fine in size. Although espresso is traditionally made with a darker roast, it is not necessary to choose a coffee bean strictly marketed as “espresso”. Dark toasts are very preferred for espresso because they are bolder and have a lower acidity when brewed. Once you have mastered the art of making coffee and espresso, you will have the opportunity to use different types of roasts to differentiate specific characteristics of coffee producing regions.
While dark roasted beans have historically been more popular in Italy, where espresso was invented, any type of coffee bean of any origin and level of roasting can be used to make espresso. Espresso is more expensive than drip coffee because it requires skills, more effort, and more expensive and complex gears to do so. When you buy a bag of coffee that says “espresso”, you almost always get dark roasted and finely ground Arabica. Espresso is made by pushing hot water through the ground coffee at extremely high pressure and speed.
Or, if you want to go far down the rabbit hole, Scott Rao's The Professional Barista's Handbook is packed with espresso theory and science. Traditionally, espresso is made with dark roasted Arabica beans with a little Robusta mixed for a better cream. Espresso is one of the most complex methods of coffee preparation, which requires serious equipment and knowledge to achieve good results.