Commonly found in Australia and New Zealand, the long black is a style of coffee made by pouring a double shot of espresso over 100-120mL of hot water. When made properly, the drink will maintain crema on top and still have a good espresso flavor. It will also still be hot, but not too hot to drink, as an iced long black starts to taste very similar to an iced americano thanks to varying amounts of ice.
To make a long black, usually you’ll first pull the hot water from the machine without any coffee added, just until you’ve gotten the correct amount of liquid. Then you pull your espresso as usual, generally adding another 50% or so tot he volume. Coffee is often consumed this way in order to “open up” the flavor, meaning to allow the complexities naturally present in the coffee beans to be appreciated as they evolve on the palate.