Duanwu Festival is one of the 3 most important festivals in China----the other 2 are  Spring Festival and  Mid-autumn Festival.The Duanwu Festival falls on the fifth day of the fifth month of the Chinese lunar calendar. For thousands of years, Duanwu has been marked by eating Zongzi and racing dragon boats.
端午节是中华民族最为重要的3个节日之一-- 其他两个是春节和中秋节。 中国农历五月初五是端午节。数千年以来，人们在端午节这一天吃粽子，赛龙舟来度过这一节日。

Ancient Chinese believed the day of Duanwu was unlucky because midsummer was just around the corner. The hot weather used to bring various diseases, which could spread rampantly. Dispelling disease and driving out evil were the main purpose of the festival. People would hang cattail and mugwort leaves on their doors to drive away mosquitoes and other insects.
古代中国人相信端午这一天是不吉利的，因为仲夏即将到来。在那时热天气经常会带来很多疾病，有的甚至是传染性很强的疾病。祛病逐妖是这个节日的主要目的。家家户户在他们的门口挂上香蒲或者艾叶以驱走蚊子和其他昆虫。

Since children are generally the most vulnerable to disease, they received extra care at this special time. Children would wear necklaces or anklet. This tradition is reserved in Shandong Province, people wear 5-colored cotton rope on the ankles of their children, which can not be taken off until the first rainfall after the festival. And the rope shall be thrown into rainwater. 
因为儿童最容易感染疾病，在这个特殊的时刻他们也受到特别的关爱。儿童们通常会在这一天戴上项链或者脚镯。在山东，端午给儿童缠五色线，一直要戴到节后第一次下雨才解下来扔在雨水里。