"Duan Wu Festival" (or the Dragon Boat Festival), the fifth day of the May in the Lunar calendar, is a important Chinese holiday. It is for remembering a politician and great poet Qu Yuan, who lived in Chu Guo Country, more than 2000 years ago. A tip on Chinese history: before the ancient China was united, it was broken into many smaller countries. Chu Guo Country was one of them.
At that time, Qu Yuan thought that his country was dying and nothing can't be done to save it. He was desperate and committed suicide by jumping into the Miluo River. It is said lots of people were looking for his body with boats, fearing that his body would be eaten by fish. Over time, this becomes the yearly Dragon Boat Contest. Also, it is said that people threw rice dumplings ("Zong Zi") into the river, so that fish would rather eat the dumplings than his body.
A rice dumpling is very different from a regular dumpling. A regular dumpling usually has veggie or meat stuffing, wrapped with flour-based wraps. The rice dumplings are usually stuffed with a variety of things, such as red bean paste, dates and meat, wrapped with glutinous rice first, then lotus leaves. In the north side of China, people love to eat sweet rice dumplings (stuffed with bean paste etc), while people from the southern part of Chins love meat based rice dumplings better.
Since the festival is to remember the dead people, on this day, we send good wishes to each other, wishing everyone healthy.