Good explanation of Thanksgiving found on Frasers blog :

Although Thanksgiving is celebrated primarily in the United States and Canada, it is also widely celebrated in six other countries around the world; Argentina, Brazil, Japan, Korea, Liberia and Switzerland. Unlike many other major holidays such as New Year’s Eve, Fourth of July, and Halloween, when people take to the streets to celebrate, Thanksgiving is much closer to heart, families and close friends gathering together to give thanks.

Most families follow traditions that begun on the first Thanksgiving between the Pilgrims and the Native Indians, but the Thanksgiving celebration has lost much of its original religious significance; instead, it now centers on cooking and sharing a bountiful meal with family and friends. In fact many have their own traditions that they follow each year. Here are some of the traditions that have become synonymous with Thanksgiving.