The name "flat white" originated in New Zealand. It's the smallest and most popular style of coffee in New Zealand, Australia, and Southeast Asia. A flat white can be made with either skim or whole milk and espresso shots of any size.
It consists of a double shot or single shot (depending on preference) of espresso topped with lukewarm froth ("froth" is the word Australians use for milky foam) which probably derives from latte art, but it has evolved to include any type fo froth. Flat whites are usually served in ceramic cups since they are traditionally more delicate beverages than other styles, such as cappuccinos or lattes.