It’s important to remember though, that coffee has changed a lot over the past few decades, so lots of people have different opinions about what exactly defines each on of these drinks. No one’s wrong necessarily, but this is how we like to make and drink these beverages today.
Espresso: It is the basic building block for almost every other drink you make.
Normally, It served in a demitasse cup (3oz). Enough ground coffee is used to extract 50-70g of espresso in 20-35 second. It depends on the coffee beans. But most baristas like to follow a ratio of 1:2 to brew espresso. For example, a 22g dose of coffee would be extracted to produce a 44g double espresso.
More about espresso Espresso Ratio
Long Black/Americano: it normally served in a cup. Double espresso
extracted on top of around 100g of hot water. The water come from espresso machine around 92-96 degree. It is too hot for majority people. Therefore, considerate baristas might mix some cooler water into their long blacks so they can be drunk sooner rather than later.
Coffee has changed a lot over the past few decades. The exact definition of what constitutes a flat white or a cappuccino has changed over the decades. The reality is that over time the humble flat white, latte and cappuccino have become more similar than different. The old style coffee, flat white should be no foam. Cafe latte was serviced in a handle glass and milk and foam were intentionally separated into layers which the consumer had to stir together before drinking. A Cappuccino with lots of dry foam on a top of cup and covered by chocolate powder.