A luau (Hawaiian lu'au) is a traditional Hawaiian feast that normally features foods such as poi, kalua pig (pork slow cooked in an imu, or earth oven), poke, and lomi salmon.
The term lu'au began to be used in the mid-1800s to refer to what was formerly called an aha'aina. It took its present name from a dish made from young taro leaves and meat or seafood baked in coconut milk.
Hawaiians living outside Hawaii will sometimes hold family parties that are as close to real Hawaiian luaus as can be managed. This can involve shipping food from the islands.
Non-Hawaiians also like to hold "luaus," but these are often Hawaiian-themed parties rather than true luaus. Guests may be given artificial leis, the party may be held poolside or oceanside on a summer evening, the drinks may be maitais, and the food and decorations may be Hawaiian-themed.
A few West coast caterers advertise "authentic" luaus.