Tangyuan or yuanxiao is a Chinese food made from glutinous rice flour mixed with a small amount of water to form balls and is then cooked and served in boiling water. Tangyuan can be either small or large, and filled or unfilled. They are traditionally eaten during Yuanxiao or the Lantern Festival,  because of a homophone for union ( 团圆 tuányuán. (quote Wikipedia)

What`s the difference between Tangyuan and Yuanxiao?

Even in China, many Chinese people consider them to be the same food, but they are different certainty. The difference between Tangyuan and Yuanxiao is the way they are made and cooked.  This is because that Chinese in different geographic areas prepare the food in different ways.

Most Northerners eat and make Yuanxiao (元宵）, its make way is contrary.  Northerners always make filling first,  and use the filling roll on the flour.Most northerners like sweet taste food, so that the  filling usually use bean paste filling.

Most Southerners eat and make Tangyuan（汤圆）, its making way like making jiaozi [dumplings, they use wet flour wrappers to fold around a filling.Most southerners like briny taste food, so that the  filling usually use meat filling.