Espresso is made by forcing steam through very fine grounds. This can be done manually, by machine, or even on a stovetop.
Grounds: for any type of espresso, you want very fine grounds, just short of powder. You won’t get this from a blade grinder, so you’ll want to make sure you have a good burr grinder.
The moka pot is a stovetop espresso maker that works by boiling water in the lower chamber, steam is forced through the coffee grounds held in the middle section, then the coffee-laden steam rises and condenses on the lid and fills the upper chamber. It’s an inexpensive way to get a decent cup of espresso.
Decent countertop machines start at around $80-100 and can easily get up into the thousands of dollars. It operates on a similar principle – converts water to steam, forces the steam under pressure through the finely ground coffee, then as the steam condenses it drains into the espresso cup. How it does this is what drives the difference in price.
Espresso machines can be manual or auto and are measured by BARs (essentially barometric pressure). You’ll want a minimum of 9 bars, 15 is better. Cheaper machines will use less than 9 bars, which will affect the quality of extraction.
Another feature of quality machines is the crema. This is the reddish froth created by a good process. It helps give the espresso a fuller flavor and longer aftertaste.
Once you’ve got a shot of espresso, there are many ways to enjoy it, each with its own name, from the straight shot of espresso, to an Americano, to a latte, and many more.