From wikipedia: A flat white is a coffee beverage prepared by pouring the creamy steamed milk from the bottom of the jug over a single shot (30ml) of espresso.
The drink is typically served in a small 150-160ml ceramic tulip cup. The stretched and texturised milk is prepared by entraining air into the milk and folding the top layer into the lower layers. To achieve the "flat", non-frothy texture the steamed milk is poured from the bottom of the jug, holding back the lighter froth on the top in order to access milk with smaller bubbles, making the drink smooth and velvety in texture.
blubarry
"According to one report, "flat white" is simply another name for a latte, and the two beverages are identical. "The only difference between the two drinks is the vessel in which they're presented. A flat white is served in a ceramic cup, usually of the same volume (200 millilitres) as a latte glass. However, some cafes will top a latte with extra froth, while others may pour a flat white slightly shorter."
So if I order a flat white, should I expect it to taste much different from a latte?