Today is the fifth day of the fifth month of the lunar calendar, which means a time for Dragon Boat Racing, hence the term Dragon Gate Festival. It also means a time for eating and the traditional food for the occasion are these yummy triangular dumplings filled with sticky rice (we call them machang where I’m from).
There are a few explanations regarding how the custom originated. One is said to be an age old tradition related to the dragon where sticky rice was thrown into the rivers as tribute to the dragon god.
Another version is that the day is meant to commemorate Qu Yuan, an acclaimed poet who claimed his own life out of despair for his country. Because the people were worried that fishes would desecrate his remains, they threw rice balls into the water instead. Sorry in advance for the spoilery details in case you happen to be watching a particular c-drama that is airing now.