Espresso has more caffeine per unit volume than most coffee beverages, but because the usual serving size is much smaller, the total caffeine content is less than a mug of standard brewed coffee, contrary to a common belief. Although the actual caffeine content of any coffee drink varies by size, bean origin, roast method and other factors, the caffeine content of "typical" servings of espresso vs. drip brew are 120 to 170 mg vs. 150 to 200 mg. The spelling "expresso" is sometimes used; while some sources state that this spelling is incorrect, other sources call it an acceptable variant spelling.

Angelo Moriondo’s Italian patent for a steam-driven "instantaneous" coffee beverage making device, which was registered in Turin in 1884 (No. 33/256), is notable. Author Ian Bersten, whose history of coffee brewers is cited below, claims to have been the first to discover Moriondo’s patent. Bersten describes the device as “… almost certainly the first Italian bar machine that controlled the supply of steam and water separately through the coffee” and Moriondo as “... certainly one of the earliest discoverers of the expresso machine, if not the earliest.” Unlike true espresso machines, it was a bulk brewer, and did not brew coffee “expressly” for the individual customer. Seventeen years later, in 1901, Luigi Bezzera, from Milan, came up with a number of improvements to the espresso machine. He patented a number of these, the first of which was applied for on the 19th of December 1901. It was titled “Innovations in the machinery to prepare and immediately serve coffee beverage” (Patent No. 153/94, 61707, granted on the 5th of June 1902). In 1905, the patent was bought by Desiderio Pavoni, who founded the “La Pavoni” company and began to produce the machine industrially (one a day) in a small workshop in Via Parini in Milan.

A distinctive feature of espresso, as opposed to brewed coffee, is espresso's association with caf?s, due both to the specialized equipment and skill required, thus making the enjoyment of espresso a social experience. Home espresso machines have increased in popularity with the general rise of interest in espresso. Today, a wide range of home espresso equipment can be found in kitchen and appliance stores, online vendors, and department stores. The first espresso machine for home use was the Gaggia Gilda. Soon afterwards, similar machines such as the Faema Faemina, FE-AR La Peppina and VAM Caravel followed suit in similar form factor and operational principles. These machines still have a small but dedicated share of fans. Until the advent of the first small electrical pump-based espresso machines such as the Gaggia Baby and Quickmill 810, home espresso machines were not widely adopted. In recent years, the increased availability of convenient counter-top fully automatic home espresso makers and pod-based espresso serving systems has increased the quantity of espresso consumed at home. The popularity of home espresso making parallels the increase of home coffee roasting. Some amateurs pursue both home roasting coffee and making espresso.

The main variables in a shot of espresso are the "size" and "length". This terminology is standardized, but the precise sizes and proportions vary substantially.

Caf?s may have a standardized shot (size and length), such as "triple ristretto", only varying the number of shots in espresso-based drinks such as lattes, but not changing the extraction – changing between a double and a triple requires changing the filter basket size, while changing between ristretto, normale, and lungo may require changing the grind, which is less easily accommodated in a busy caf?, as fine tweaking of the grind is a central aspect to consistent quality espresso-making.

Cold espresso (espresso freddo) is an alternative form of espresso, mostly served in southern Europe. Conceived in Greece, along with cappuccino freddo around the early '90s, freddo espresso enjoys great demand in Greece and its neighbouring countries during summer. The process of making it appears to be simple; after preparing 2 shots of espresso (usually Ristretto), the coffee is being stirred in a big iron can along with sugar (if necessary) and 2-3 ice cubes until the can is cold. Then, the blend is put in a glass full of ice cubes.