There are no differences between a groundhog and a woodchuck. Both names are used to refer to the same animal. In some parts of the world, groundhogs are known as "whistle-pigs" and "land-beavers."
Groundhogs are rodents belonging to the family Sciuridae, a large group of ground squirrels called marmots. These animals spend their summers eating as much as they can so they can survive a long winter hibernation. Because of the groundhog hibernates from the first frost until spring, the animal is the focus of Groundhog Day every February. The tradition states that should the groundhog see his shadow when he comes out of hibernation, six more weeks of winter are sure to follow.