There are many legends about the origins of Dragon Boat Festival. But the most popular story is Qu Yuan version which is widely accepted in China.
To commemorate the death of poet Qu Yuan 
Ququan( 340B.C.—278B.C.) was born in a noble family of the ancient state of Chu. When he served as a minister in the government, he claimed to hire the capable brains and improve the interior affairs policies; clearly, he supported the idea of uniting the state of Qi to against the state of Qin which was getting powerful day by day. But, some ministers like Zilan(子兰) and Jin Shang(靳尚) as well as the imperial concubine Zheng Xiu(郑袖) were bribed by Qin’s emissary Zhang Yi(张仪).Persuaded by these dogs, the King of Chu ignored Qu’s strategy and banished him. As a result, the King was induced to the State of Qin where he was imprisoned until die. The successor still didn’t put QuYuan in an important position and continue banishing Qu to the regions south of the Yangtze River. During the banishment, Qu Yuan had written a number of poems which expressing his ideal state. In 278 BC, Baiqi(白起),the senior general of Qin, conquered the capital of Chu. So disappointed and helpless, Qu Yuan killed himself by jumping into the Miluo River(汨罗江) on the fifth day of the fifth lunar month.
As soon as the local people heard the news that Qu Yuan committed suicide, they made great efforts to save the poet, boating along the river to the Dongting Lake. However, no matter how hard they tried, they still could not find the body. After boating and searching in the rain for a long time, the upset people were afraid that fish would treat the poet’s body as a meal, so some of them hurried back home to bring rice dumplings then threw them into the river; the rest kept paddling oars to scare the fish away. Gradually, it developed into the customs of dragon boat racing and eating Zongzi(rice dumpling).
To commemorate the death of Wu Zixu 
Wu Zixu(伍子胥559B.C.—484B.C.)was born in the state of Chu. His father and elder brother were involved in a political conspiracy and killed by the king of Chu. So Wu Zixu fled to the state of Wu. The love to the mother land was replaced by revenge. He devoted himself to the Wu’s extension. Like a gifted strategist, he conquered the capital of Chu in five wars and consolidated his influence in the government of Wu. With his outstanding talent，the state of Wu got more powerful and conquered the state of Yue after Fuchai becoming the king. However, no hero can pass the barrier of beauty; Fuchai was totally infatuated with the Yue girl Xishi who was titled the first of the four beauties in ancient China. Hence, Zixu was forced to commit suicide by the king Fuchai.Before his death, he requested a neighbor to hang his eyes on the city gate of Wu because he knew Yue would conquer Wu some day. This saying pissed the king off; he ordered to throw Wu Zixu’s body into the river on the fifth day of the fifth month. Then, in order to remember Wu Zixu, Suzhou people changed the name of the river into Xu River.
To commemorate the death of Cao E
This theory appears on <Cao E’ stele> of the Eastern Han Dynasty (25-220). Cao’s father drowned himself in the river accidently when he was presiding over a ceremony commemorating Wu Zixu during the Duanwu Festival.Cao E(曹娥,A.D.130-A.D.143), only 14 years old, crying while walking along the river days and nights. Even, 17 days passed, her father’s body still cannot be found. So the little girl jumped into the river. Five days later, her body and his father’s body were both found at the river. For praising and promoting Cao’s fealty，a temple had been built in her hometown Shangyu and the river also had been changed into Cao E River.
The day full of evil
In the Pre-Qin Period, there was an old saying among the common people: May was the hottest month and the fifth day of May was the worst day ever. It is said that the five poisonous creatures always came out on this day. And if a baby was born on this day, it was definitely not a good omen at all; it might even be harmful to the parents. So, it really made sense when people inserted calamus or drank realgar wine this day for they just tried to drive evil away.

Eating Zongzi:
Zongzi (粽子)is a very traditional Chinese food for Dragon Boat Festival. It was made of glutinous rice.Before eating, you need to steam or boil it. To the western foreigners, they get another name which is rice dumpling. There are two sayings about Zongzi. One is related to Qu Yuan, because people who admired Qu Yuan threw many rice dumplings into the river to keep the fish away; the other is about the dragon that lived under the river, once he gets the delicious Zongzi, he would not hurt any person.
For thousand years, the Zongzi we could see today have already changed a lot in both shapes and fillings. In the north of China, it was wrapped in reed leaves and shaped in triangle; while in the south, it was wrapped with bamboo leaves and shaped in tetrahedral.The steamed Zongzi with fresh bamboo flavor always make people mouth watering. The fillings used for Zongzi can reflect region features. Different from the south, the fillings in northern part are very sweet, like red beans, dates while the fillings vary from meat, egg yolk, to chestnuts in the southern part. The famous brand of Zongzi is Wufangzhai(五芳斋).
Making Zongzi need family members work together and wrapping is really a skillful job. In my point of view, if you have a chance to learn how to make Zongzi, just go for it. Can you imagine how the shape will be like? Prove it! 

By the way, a quick question, do you know the traditional food for Qingming Festival, Mid autumn Day and Chinese New Year?

Xionghuangjiu	Ay-tscao and calamus on the door	perfumed medicine bags