Bánh bao (literally "enveloping cake") is a ball-shaped dumpling containing pork or chicken meat, onions, eggs, mushrooms and vegetables, in Vietnamese cuisine. Additionally the steamed bun often has Chinese sausage and a portion of a hard-boiled egg inside.
The dish originated with the baozi from China but was adapted by the Vietnamese and is also available in most other countries with significant Vietnamese populations. Bánh bao are generally smaller than baozi, and are filled with savory fillings, the most popular of which is seasoned ground pork. As in China, pork is the most popular kind of meat in Vietnam. Vegetarian version of banh bao also exists.
Bánh bao is an old fashioned Cantonese dim sum called tai pao (大包, literally "big bun") brought to Vietnam by Cantonese immigrants. It was invented during the hardship days of old China to feed the ordinary people.
See also 
Grilled Bánh Bao: Bánh Bao Nướng
Sweet Bánh Bao: Bánh Bao Chỉ