Espresso

Espresso is several things at once. It is a unique method of brewing in which hot water is forced under pressure through tightly packed coffee, one or two servings at a time. It is a roast of coffee, darker brown than the traditional American roast but not extremely dark. In a larger sense, it is an entire approach to coffee cuisine, involving not only roast and brewing method, but grind and grinder, a technique of heating and frothing milk, and a traditional menu of drinks. In the largest sense of all, it is an atmosphere or mystique: The espresso brewing machine is the spiritual heart and esthetic centerpiece of the great coffee places, the cafés, caffes and coffee houses of the world.

The espresso system was developed in and for cafés and caffes. Despite advances in inexpensive home espresso systems, it is still difficult to duplicate the finest caffe espresso or cappuccino in your kitchen or dining room without spending several hundred dollars on equipment.

Fundamentally, they make coffee as any other brewer does: by steeping ground coffee in hot water. The difference is the pressure applied to the hot water. In normal drip brewing processes, the water seeps by gravity down through ground coffee, loosely spooned into a filter. In the espresso process, the water is forced under pressure through very finely ground coffee packed tightly over the filter.

Information Source: Coffee Review and Image Source: Wikipedia